Abstract:
An electrical connector has a base defining a plurality of aperture spaces therein. A plurality of contacts are received and secured within the aperture spaces, and include signal contacts and ground contacts. In addition, a plurality of ground shields are received and secured within the aperture spaces. The ground shields are positioned to shield selected ones of the signal contacts from noise and/or cross-talk generated by other signal contacts within the base. Each ground shield has an electrical contact site at which the ground shield is in physical and electrical contact with a ground contact. The electrical contact site is flexible.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application contains subject matter related to the subject matter disclosed in U.S. patent application Ser. No. 08/942,084, filed Oct. 1,1997; U.S. patent application Ser. No. 09/045,660, filed Mar. 20,1998; U.S. patent application Ser. No. 09/295,504, filed Apr. 21, 1999, now U.S. Pat. No. 6,116,926; and U.S. patent application Ser. No. 09/302,027, filed Apr. 29,1999, each of which is hereby incorporated by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to a header assembly for mounting to a circuit substrate and for receiving a complementary electrical connector. In particular, the present invention is for a high density header assembly for use in, for example, a motherboard in a backplane/back panel application.  
         BACKGROUND OF THE INVENTION  
         [0003]    In a typical electrical interconnection system, a first removably insertable circuit board includes a complementary electrical connector that is to be mated with a header assembly or header which is mounted to a second circuit board. As should be understood, when the first circuit board is coupled to the second circuit board by way of the electrical connector and header and when the first circuit board is in operation, a number of signals enter or leave the first circuit board through conductive paths defined by the electrical connector on the first circuit board and the header on the second circuit board. In many instances, the second circuit board has other circuit boards coupled thereto by other respective headers and complementary electrical connectors, and the aforementioned signals can originate from or be destined for such other circuit boards. Of course, the aforementioned signals can also originate from or be destined for other locations remote from the second circuit board by way of appropriate interconnections.  
           [0004]    If it is desirable to suppress signal noise and/or cross-talk, it is known that a signal may be transmitted over a pair of differential (positive and negative) signal lines that travel together in close proximity. Typically, in such pair of differential lines, the signal itself (+V) is transmitted on the positive line, and the negation of the signal (−V) is transmitted on the negative line. Since both lines travel together in close proximity, any noise encountered by the lines should appear in a generally identical form on both lines. Accordingly, the subtraction (by appropriate circuitry or other means) of the negative line (−V+noise) from the positive line (+V+noise) should cancel out such noise ((+V+noise)−(−V+noise)=2V), thus leaving the original signal, perhaps with a different amplitude.  
           [0005]    Oftentimes, in a high frequency environment, most every signal passing to and from a circuit board travels as a pair of differential signals on a pair of differential signal lines. Accordingly, the electrical connector on the circuit board and the header on the backplane must accommodate all such pairs of differential signal lines. Moreover, with increased contact density on a circuit board, there has been a corresponding increase in signal lines associated with such circuit board. As a result, the number of individual lines running through the electrical connector of the circuit board and the associated header can be quite large. At the same time, since it is desirable to increase the number of circuit boards that can be coupled to the backplane, the ‘real estate’ on the backplane used by the header must be kept small. Therefore, the ‘density’ of individual signals that pass through the electrical connector and header must be increased.  
           [0006]    With such increased density, however, the issue of susceptibility to noise and/or cross-talk again arises, even in electrical connectors and headers that transmit pairs of differential signals. To combat such density-based noise, the header in particular has been modified to include ground shielding which substantially electromagnetically isolates within the header each pair of differential signal lines from every other pair of differential signal lines.  
           [0007]    Accordingly, a need exists for a header that can have multiple differential signal pairs in relatively high density, and that has ground shielding for the signal pins, where the header is practical and relatively easily manufactured.  
           [0008]    An example of such a header is disclosed in U.S. patent application Ser. No. 09/302,207, as was disclosed and incorporated by reference above. Such a header has proven to be remarkably capable of reducing noise and/or cross-talk. However, the particular design of the header disclosed in such application does not have an especially high tolerance for margins of error in dimensions of parts thereof. For example, the features responsible for maintaining interference fits of such parts are not flexible, and accordingly, fail to in fact effectuate such interference fits if not dimensionally precise.  
           [0009]    That is, most header parts are inserted into apertures in a header base and held therein by interference fits assisted by various interfacing bumps on the parts. In particular, if an aperture in the header base is slightly too wide, or if an interfacing bump on a part that is to be inserted into the aperture is slightly too short, such bump will not contact the inner wall of such aperture once the part is inserted, and will not help to hold the part within the aperture by way of an interference fit. As a result, intermittent electrical connection could occur. Also, the part can fall out of the base. Conversely, if an aperture in the header base is slightly too narrow, or if an interfacing bump on a part that is to be inserted into the aperture is slightly too tall, such bump will exert excessive force on the inner wall of such aperture once the part is inserted, and may in fact result in excessive strain on the base which can lead to immediate or eventual structural failure. As a result, the header is destroyed.  
           [0010]    Accordingly, and moreover, a need exists for such a header wherein the header has a relatively high tolerance for margins of error in dimensions of parts thereof.  
         SUMMARY OF THE INVENTION  
         [0011]    The present invention satisfies the aforementioned need by providing an electrical connector that has a base defining a plurality of aperture spaces therein. A plurality of contacts are received and secured within the aperture spaces, and include signal contacts and ground contacts. In addition, a plurality of ground shields are received and secured within the aperture spaces.  
           [0012]    The ground shields are positioned to shield selected ones of the signal contacts from noise and/or cross-talk generated by other signal contacts within the base. Each ground shield has an electrical contact site at which the ground shield is in physical and electrical contact with a ground contact. The electrical contact site is flexible. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The foregoing summary, as well as the following detailed description of preferred embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. As should be understood, however, the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:  
         [0014]    [0014]FIG. 1 is a plan view of a connector side of a header, and shows such header mounted to a backplane;  
         [0015]    [0015]FIG. 2 is a perspective view of a portion of the pins and ground shields of the header of FIG. 1, with the shroud of FIG. 1 removed for clarity;  
         [0016]    [0016]FIG. 3 is the same perspective view of FIG. 2, but shows only the pair of differential signal pins of FIG. 2;  
         [0017]    [0017]FIG. 4 is the same perspective view of FIG. 2, but shows only the ground pins of FIG. 2;  
         [0018]    [0018]FIG. 5 is the same perspective view of FIG. 2, but shows only the ground shields of FIG. 2;  
         [0019]    [0019]FIG. 6 is a perspective view showing a ground pin and a pair of ground shields in accordance with an alternate embodiment of a header;  
         [0020]    [0020]FIG. 7 is a perspective view similar to that of FIG. 2, but from a different angle, and shows another embodiment of a header which is similar to the embodiment as shown in FIGS.  1 - 5 , wherein primary and secondary headers share common pins and sandwich the backplane therebetween;  
         [0021]    [0021]FIG. 7A is an exploded perspective view showing the primary header, backplane, and secondary header of FIG. 7;  
         [0022]    [0022]FIG. 7B is a perspective view showing a securing contact employed in connection with the secondary header of FIG. 7;  
         [0023]    [0023]FIG. 8 is a plan view of a portion of the connector side of a header similar to the header of FIG. 1 in accordance with an embodiment of the present invention;  
         [0024]    [0024]FIG. 9 is a cross-sectional view taken along the line  9 - 9  of FIG. 8, and shows the grounds shields of the header of FIG. 8;  
         [0025]    [0025]FIG. 10 is a plan view of a portion of the connector side of a header similar to the header of FIG. 1 in accordance with another embodiment of the present invention;  
         [0026]    [0026]FIG. 11 is a cross-sectional view taken along the line  11 - 11  of FIG. 10, and shows the grounds shields of the header of FIG. 10;  
         [0027]    [0027]FIG. 12 is a plan view of a portion of the connector side of a header similar to the header of FIG. 1 in accordance with still another embodiment of the present invention;  
         [0028]    [0028]FIG. 13 is a cross-sectional view taken along the line  9 - 9  of FIG. 8, and shows the grounds shields of the header of FIG. 8;  
         [0029]    [0029]FIG. 14 is a plan view of a portion of the connector side of a header similar to the header of FIG. 1 in accordance with even still another embodiment of the present invention;  
         [0030]    [0030]FIG. 15 is a cross-sectional view taken along the line  9 - 9  of FIG. 8, and shows the grounds shields of the header of FIG. 8;  
         [0031]    [0031]FIG. 16 is a plan view of a portion of the connector side of a header similar to the header of FIG. 1 in accordance with still further another embodiment of the present invention; and  
         [0032]    [0032]FIG. 17 is a cross-sectional view taken along the line  9 - 9  of FIG. 8, and shows the grounds shields of the header of FIG. 8. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0033]    Certain terminology may be used in the following description for convenience only and is not considered to be limiting. For example, the words “left”, “right”, “upper”, and “lower” designate directions in the drawings to which reference is made. Likewise, the words “inwardly” and “outwardly” are directions toward and away from, respectively, the geometric center of the referenced object. The terminology includes the words above specifically mentioned, derivatives thereof, and words of similar import.  
         [0034]    Referring to the drawings in detail, wherein like numerals are used to indicate like elements throughout, there is shown in FIG. 1 a header assembly or header  10 . The header  10  as shown in FIG. 1 and FIGS.  2 - 7 B is disclosed in U.S. patent application Ser. No. 09/302,207, as was disclosed and incorporated by reference above, and is discussed herein for background and reference purposes. As seen, the header  10  is mounted to a circuit substrate such as a backplane  12  in a position to receive a complementary electrical connector (not shown) on a circuit board (not shown) to be coupled to the backplane  12  by way of the electrical connector and header  10 .  
         [0035]    As seen, the header  10  includes an insulating shroud  14  which has a base  16 . As should be understood, when the header  10  is mounted to the backplane  12 , the base  16  of the shroud  14  of the header  10  is generally parallel to such backplane  12 . Typically, although not necessarily, the shroud  14  of the header  10  also has walls  18  that extend away from the base  16  at generally right angles thereto. Accordingly, the walls  18  form a well within which the electrical connector is inserted while mating to the header  10 . Typically, the walls  18  align and guide the electrical connector as it is being inserted so as to ensure a proper connection and so as to prevent damage that may occur from mis-alignment. The walls  18  may include one or more keying elements (the slots shown, for example) that mate to corresponding keying elements in the electrical connector to further ensure a proper connection and for polarization.  
         [0036]    As should be understood, and as seen in FIG. 1, the base  16  of the shroud  14  has a connector side  20  that faces toward the mating connector, and a backplane side  22  that faces toward the backplane  12 . The base  16  of the shroud  14  also has a primary edge  23 , which as will be explained below is designated as such for purposes of being a fixed reference in the present disclosure. As seen in FIG. 1, the primary edge  23  runs along the top of the base  16 .  
         [0037]    Header  10  includes signal contacts, ground contacts, and ground shields. In a differential pair application such as that shown in FIG. 1, the header  10  has a plurality of pairs  24   p  of differential signal pins  24   a ,  24   b , a plurality of ground shields  26 , and a plurality of ground pins  28 . As should be understood, for purposes of clarity, only a few of the elements  24   a ,  24   b ,  24   p ,  26  and  28  are shown in detail, while the remainder of such elements are shown in phantom. As seen, each pair  24   p  of signal pins  24   a ,  24   b , each ground shield  26 , and each ground pin  28  is mounted to the base  16  of the shroud  14 . Each signal pin  24   a ,  24   b  and each ground pin  28  extends away from the base  16  from both the connector side  20  and the backplane side  22  in opposing directions generally perpendicular to such base  16 , as can be seen in and/or appreciated from FIGS.  1 - 4 .  
         [0038]    Alternatively, in the case where the header  10  is to be surface mounted to the backplane  12  (not shown), each signal pin  24   a ,  24   b  and each ground pin  28  may extend away from the base  16  from the connector side  20  only. Any surface mounting technology may be employed in such a circumstance without departing from the spirit and scope of the present invention. For example, Ball Grid Array technology such as that disclosed in PCT Publication No. WO 98/15991, hereby incorporated by reference, may be employed.  
         [0039]    As can be seen in FIG. 1, the pairs  24   p  of signal pins  24   a ,  24   b  are arranged into a plurality of rows  30  extending in a first direction (as indicated by the arrow R) along the base  16  and along the primary edge  23  of the base  16 . That is to say, the rows  30  and the first direction run along the surface of the base  16 , and generally parallel to the primary edge  23 . Additionally, the pairs  24   p  of signal pin  24   a ,  24   b  are further arranged into a plurality of columns  32   a  that extend in a second direction (as indicated by the arrow C) along the base  16  generally perpendicular to the first direction. Again, that is to say, the columns  32   a  and the second direction run along the surface of the base  16 , and generally perpendicular to the primary edge  23 . To summarize, then, the pairs  24   p  of signal pins  24   a ,  24   b  are arranged generally rectilinearly.  
         [0040]    Still referring to FIG. 1, the signal pins  24   a ,  24   b  in each pair  24   p  are adjacently arranged into a sub-row that extends in the first direction (arrow R). Accordingly, each row  30  has X pairs  24   p  of signal pin  24   a ,  24   b  and 2X individual signal pins  24   a ,  24   b . Correspondingly, each column  32  has Y pairs  24   p  of signal pins  24   a ,  24   b , and 2Y individual signal pins  24   a ,  24   b.    
         [0041]    As seen in FIGS.  1 - 3 , each signal pin  24   a ,  24   b  in a pair  24   p  has an inner side  34   i  that faces toward the other signal pin  24   a ,  24   b  in the pair  24   p , an outer side  34   o  opposite the inner side  34   i , a primary side  34   p  that extends between the inner side  34   i  and the outer side  34   o  and that faces toward the primary edge  23  of the base  16 , and a non-primary side  34   a  that extends between the inner side  34   i  and the outer side  34   o  and that faces away from the primary edge  23  of the base  16 .  
         [0042]    Each signal pin  24   a ,  24   b  (and each ground pin  28  as well) as shown in the drawings is generally rectilinear in transverse cross-section, and accordingly the sides  34   i ,  34   o ,  34   p ,  34   a  of each signal pin  24   a ,  24   b  (and the sides of each ground pin  26 ) are generally flat as shown. However, it will be appreciated that the signal pins  24   a ,  24   b  (and the ground pins  26 ) can have other configurations in transverse cross-section, including but not limited to circular, oblong, and multi-sides other than four. Nevertheless, the sides  34   i ,  34   o ,  34   p ,  34   a  of each signal pin  24   a ,  24   b  as designated above are still applicable even if such sides do not correspond to flat surfaces in transverse cross-section.  
         [0043]    Although the present invention is described in terms of pairs  24   p  of differential signal pins  24   a ,  24   b , it will be recognized that other arrangements or types of signal pins may be employed without departing from the spirit and scope of the present invention. For example, and depending on the particular application, the signal pins may be individually grouped (in a single-ended arrangement), or may be grouped into threes, fours, fives, etc.  
         [0044]    Referring now to FIGS. 1, 2, and  5 , in the embodiment of the header  10  shown, at least one ground shield  26  is associated with each signal pin  24   a ,  24   b . Preferably, each ground shield  26  generally extends through the base  16  between the connector side  20  and the backplane side  22 , and more preferably from about the surface of the connector side  20  to about the surface of the backplane side  22 . Accordingly, each ground shield  26  preferably has a depth that generally corresponds to a thickness of the base  16  of the shroud  14 . As a result, though not shown in FIGS.  2 - 5 , it should be apparent where the base  16  of the shroud  14  is positioned in relation to the signal pins  24   a ,  24   b , ground shields  26 , and ground pins  28 .  
         [0045]    Preferably, each ground shield is generally L-shaped and includes first and second attached wings  36   a ,  36   b  that are arranged at about right angles with respect to each other. The first wing  36   a  of each ground shield  26  may extend generally along the first direction (arrow R) adjacent and along the primary side  34   p  or the non-primary side  34   a  of the associated signal pin  24   a ,  24   b . Of course, to achieve shielding of each pair  24   p  of signal pins  24   a ,  24   b , it is necessary that some order be provided with regard to which side (primary  34   p  or non-primary  34   a ) each first wing  36   a  extends. As but one example, each ground shield  26  associated with a signal pin  24   a  (to the left in FIG. 1) may extend along the primary side  34   p  thereof, and each ground shield  26  associated with a signal pin  24   b  (to the right in FIG. 1) may extend along the non-primary side  34   a  thereof.  
         [0046]    Preferably, the first wings  36   a  of all the ground shields  26  extend adjacent and along one or the other of the primary side  34   p  and the non-primary side  34   i  of the respective associated signal pins  24   a ,  24   b . As shown, the first wings  36   a  of all the ground shields  26  extend adjacent and along the primary side  34   p  of the respective associated signal pins  24   a ,  24   b . However, and as was discussed above, in certain circumstances an alternate arrangement may be useful.  
         [0047]    As seen in FIGS. 1, 2, and  5 , the second wing  36   b  of each ground shield  26  generally extends along the second direction (arrow C) adjacent and along the outside  34   o  of the associated signal pin  24   a ,  24   b . With the plurality of ground shields  26  thus arranged with respect to the pairs  24   p  of signal pins  24   a ,  24   b , then, and as best understood by viewing FIG. 1, the plurality of ground shields  26  in combination substantially electromagnetically isolate within the base  16  of the shroud  14  each pair  24   p  of signal pins  24   a ,  24   b  from every other pair  24   p  of signal pin  24   a ,  24   b.    
         [0048]    Preferably, for each pair  24   p  of signal pins  24   a ,  24   b , the first wings  36   a  of the associated ground shields  26  extend toward each other and reside generally in a single plane. Preferably, such first wings  36   a  do not actually contact each other, and the distal end of each second wing  36   b  does not extend so far as to directly contact another ground shield  26 . Accordingly, portions of the material forming the base  16  separate the ground shields  26  from one another, and in doing so provide structurally integrity to such base  16 . Due to the lack of direct connections between ground shields  26 , and as can be appreciated from FIGS. 1, 2, and  5 , unshielded gaps exist between the ground shields. Such gaps should be minimized so that the pairs  24   p  of signal pins  24   a ,  24   b  are adequately shielded.  
         [0049]    As shown in FIG. 1, except for the pairs  24   p  in the bottom-most row  30 , each pair  24   p  of signal pins  24   a ,  24   b  is substantially surrounded on all sides by ground shields  26 . In particular, the outer sides  34   o  and primary sides  34   p  of the signal pins  24   a ,  24   b  are substantially surrounded by the first and second wings  36   a ,  36   b  of the associated ground shields  26 , and the non-primary sides  34   a  of the signal pins  24   a ,  24   b  are surrounded by the ground shields  26  associated with the pair  24   p  of signal pin  24   a ,  24   b  immediately below. Since differential pairing is used, shielding between each signal pin  24   a ,  24   b  in each pair  24   p  is not believed to be necessary. If a single-ended arrangement is used, however, shielding between each row of signals may be used. The pairs  24   p  of signal pin  24   a ,  24   b  in the bottom-most row do not have shielding in the direction of the non-primary sides  34   a . However, no other signal pins  24   a ,  24   b  are in the immediate vicinity in such un-shielded direction to create noise and/or cross-talk in the pairs  24   p  of signal pin  24   a ,  24   b  in the bottom-most row.  
         [0050]    Preferably, and as can be seen from FIGS. 1, 2, and  5 , each ground shield  26  is generally identical to every other ground shield  26 . Moreover, each ground shield  26  is symmetrical such that it can be placed adjacent a signal pin  24   a  or  24   b . Accordingly, only one type of such ground shield  26  is necessary in constructing the header  10  as shown. As best seen in FIGS. 2 and 5, each ground shield  26  is of a relatively simple design and in fact may be stamped from an appropriate sheet of conductive material into a final form by known forming and/or stamping processes. Alternatively, each shield  26  may be molded or extruded by known processes.  
         [0051]    Preferably, the shroud  14  of the header  10  is molded from a suitable insulative material such as a high temperature plastic into a final form by known processes, where such final form includes defined apertures for each signal pin  24   a ,  24   b , each ground shield  26 , and each ground pin  28 . Also preferably, each ground shield  26  is inserted into the base  16  of the shroud  14  from either the connector side or backplane side  22 , preferably by mechanical means, and such ground shield  26  maintains an interference fit with such base  16  of such shroud  14 . Preferably, the first or second wing  36   a ,  36   b  (the first wing  36   a  in FIGS. 2 and 5) of each ground shield  26  includes a bump  38   a  at a surface thereof to assist in maintaining the aforementioned interference fit of the ground shield  26  with the base  16  of the shroud  14 .  
         [0052]    Alternatively, each signal pin  24   a ,  24   b , each ground shield  26 , and/or each ground pin  28  may be over-molded in situ during formation of the base  16  and shroud  14 . However, it is presently believed that such in situ over-molding may be excessively complicated when compared to other available manufacturing techniques.  
         [0053]    Preferably, each ground pin  28  electrically contacts at least one ground shield  26  at the second wing  36   b  thereof. More preferably, and as shown in FIGS. 1 and 2, such contact occurs at the outer surface (the surface away from the associated signal pin  24   a ,  24   b ) of such second wing  36   b . Preferably, every ground shield  26  electrically contacts a ground pin  28 . Presumably, at some location, either in the complementary electrical connector, the mother board, or in another circuit, each ground pin  28  is electrically grounded. Accordingly, the ground shields  26  electrically contacted by the ground pins  28  are also grounded and are electrically coupled to one another. Although described up to now as rigid bumps  38   a ,  38   b , other types of retention features may be employed without departing from the spirit and scope of the present invention. For example, one or both wings  36   a ,  36   b  in each ground shield  26  could include a compliant section (not shown) to retain such ground shield  26  in the base  16  of the shroud  14  and/or to retain an associated ground pin  28  in such base  16  of such shroud  14 .  
         [0054]    Preferably, and as best seen in FIGS. 2 and 4, each ground pin  28  includes a generally planar fin  40  that generally resides within the base  16  of the shroud  14  and that extends generally laterally from the main body of the ground pin  28 . As seen in FIG. 1, the fin  40  extends generally in the second direction (arrow C), and has generally opposing planar sides  42  (FIGS. 2, 4). Accordingly, each ground shield  26  is electrically contacted by a ground pin  28  at a planar side  42  of the fin  40  of such ground pin  28 .  
         [0055]    Preferably, the ground pins  28  are arranged into a plurality of rows  30  that extend in the first direction (arrow R), and a plurality of columns  32   be ,  32   bi  that extend in the second direction (arrow C). As seen in FIG. 1, each row  30  of ground pins  28  corresponds to a row  30  of signal pin  24   a ,  24   b , and each column  32   be ,  32   bi  of ground pins  28  alternates with a column  32   a  of pairs  24   p  of signal pins  24   a ,  24   b . As seen, columns  32   be  of ground pins  28  are a pair of exterior or outer-most columns (left and right) and columns  32   bi  of ground pins  28  are at least one interior column (four are shown in FIG. 1) positioned between such exterior columns  32   be . Preferably, each ground pin  28  in each interior column  32   bi  is positioned between and electrically contacts first and second ground shields  26  on either lateral side of such ground pin  28 . As will be described below, each ground pin  28  in each interior column  32   bi  preferably contacts bumps  38   b  on wings  36   b  of such first and second ground shields  26 . Also preferably, each ground pin  28  in each exterior column  32   be  is positioned adjacent and electrically contacts only a single ground shield  26  on one lateral side thereof.  
         [0056]    In the case of a ground pin  28  in one of the interior columns  32   bi , it is seen from FIG. 1 that the first ground shield  26  corresponding to such ground pin  28  is associated with a signal pin  24   a ,  24   b  of a first pair  24   p  of signal pins on one side of the ground pin  28  (the left side, for example), the second ground shield  26  is associated with a signal pin  24   a ,  24   b  of a second pair  24   p  of signal pin  24   a ,  24   b  on the other side of the ground pin  28  (the right side, to continue the example), and the first and second ground shields  26  electrically contact the ground pin  28  at either planar side of the fin  40  thereof. As seen, then, the first and second pairs  24   p  of signal pins  24   a ,  24   b  both reside in a row  30  that corresponds to the row  30  of the ground pin  28  at issue; more precisely, such ground pin  28  and such first and second pairs  24   p  of signal pin  24   a ,  24   b  can be considered to reside in a single row  30  (although not necessarily linearly aligned within the row  30 ). As also seen, such first and second pairs  24   p  of signal pins  24   a ,  24   b  respectively reside in immediately adjacent columns  32   a  on either side of the column  32   bi  of the ground pin  28  at issue.  
         [0057]    In the case of a ground pin  28  in one of the exterior columns  32   b e, it is also seen from FIG. 1 that the single ground shield  26  corresponding to such ground pin  28  is associated with a signal pin  24   a ,  24   b  of a single pair  24   p  of signal pins on one side of such ground pin  28 , and the single ground shield  26  electrically contacts the ground pin  28  at one planar side of the fin  40  thereof. Similar to the previous case, the single pair  24   p  of signal pins  24   a ,  24   b  resides in a row  30  corresponding to the row  30  of such ground pin  28 . In this case, the single pair  24   p  of signal pins  24   a ,  24   b  resides in an immediately adjacent column  32   a  on only one side of the column  32   be  of such ground pin  28 .  
         [0058]    In either case, each ground pin  28  is preferably inserted into the base  16  of the shroud  14  from either the connector side or backplane side  20 ,  22  thereof, as with the ground shields  26 . Such operation may be performed by appropriate automatic insertion machinery. Preferably, each ground pin  28  in the interior columns  32   bi  maintains an interference fit between contacted second wings  36   b  of the first and second ground shields  26 , and more preferably between contacted bumps  38   b  on such second wings  36   b . Correspondingly, it is preferable that each ground pin  28  in the exterior columns  32   be  maintains an interference fit between the contacted second wing  36   b  of the single ground shield  26  and with an interior surface of the base  16  (not shown) where such interior surface is opposite the contacted second wing  36   b  of the single ground shield  26 . Preferably, and as best seen in FIGS. 2 and 5, each second wing  36   b  of each ground shield  26  includes a bump or bumps  38   b  at a contact surface thereof (the outer surface as shown in FIGS. 1, 2, and  5 ) to assist in electrically contacting the ground pin  28  at the fin  40  thereof, and to assist in maintaining the aforementioned interference fit.  
         [0059]    As with the ground pins  28  and ground shields  26 , each signal pin  24   a ,  24   b  is preferably inserted into the base  16  of the shroud  14  from either the connector side or backplane side  20 ,  22  thereof, and preferably maintains an interference fit with such base  16 . Such insertion operation may be performed by appropriate automatic insertion machinery. More preferably, all of the aforementioned elements are inserted into the base  16  of the shroud  14  from the backplane side  22 . As should be understood, the backplane side  22  is more readily accessible since it is not obstructed by any walls  18 . Moreover, insertion from the backplane side  22  locks pins  24   a ,  24   b ,  28  in place upon securing the header  10  to the backplane  12 . Preferably, and as seen in FIGS. 2 through 4, each signal pin  24   a ,  24   b  and each ground pin  28  preferably includes various contact surfaces that assist in maintaining an interference fit directly with the base  16  of the shroud  14 .  
         [0060]    Preferably, each signal pin  24   a ,  24   b  and each ground pin  28  includes a compliant section  44  exterior from the base  16  adjacent the backplane side  22  thereof, as best seen in FIGS.  2 - 4 . As should be understood, each compliant section  44  maintains an interference fit with plated through holes in the backplane  12  when the header  10  is mounted thereto. As should be appreciated, it is undesirable to insert the compliant sections  44  into the base  16  of the shroud  14 . Such compliant portions  44  may deform or likely would not easily fit through such base  16  during such insertion.  
         [0061]    In one embodiment of the header  10 , and referring again to FIG. 1, each signal pin  24   a ,  24   b  and each ground pin  28  in transverse cross-section is approximately 0.4 mm by 0.4 mm in width and height, in the region of the main pin portions that are received by the complementary electrical connector. Additionally, in such embodiment, each ground shield  26  has a main thickness of about 0.2 mm. Accordingly, if each signal pin  24   a ,  24   b  and each ground pin  28  in a row  30  is spaced about 1.0 mm in the first direction (arrow R), each signal pin  24   a ,  24   b  may be separated from its corresponding ground shield  26  by about 0.4 mm. Such distance is sufficient to provide a reasonable degree of structural integrity to the base  16  of the shroud  14 .  
         [0062]    Referring now to FIG. 6, it is seen that in an alternate embodiment of the header  10 , each ground pin  28 ′ does not have the fin  40  of the ground pin  28  (FIGS. 2 and 4), and each ground shield  26 ′ does not have the contacting bump(s)  38   b  of the ground shield  26  (FIGS. 2 and 5). Instead, each ground shield  26 ′ includes an integral tab  46  that contacts a contact portion  48  of the ground pin  28 ′, where the contact portion  48  is generally in-line with respect to the longitudinally extending ground pin  28 ′. Preferably, the tab  46  is formed within the ground shield  26 ′ by an appropriate stamping or molding operation, and the tab  46  is inclined slightly away from the main body of the ground shield  26 ′ and toward the ground pin  28 ′. Accordingly, the tab  46  is urged into good electrical contact with the contact portion  48  when the ground pin  28 ′ and the ground shield  26 ′ are mounted to the base  16  of the shroud  14  (not shown in FIG. 6). As shown, the ground pin  28 ′ is for an interior column  32   bi  since two ground shields  26 ′ flank such ground pin  28 ′. Of course, only one ground shield  26 ′ would flank the ground pin  28 ′ if such ground pin  28 ′ were in an exterior column  32   be.    
         [0063]    Referring now to FIG. 7, it is seen that in another embodiment of the header  10  which is similar to the embodiment as shown in FIGS.  1 - 5 , a primary header  10   a  has pairs  24   p  of signal pins  24   a ,  24   b  and ground pins  28  that extend a relatively longer distance (as compared with the header  10  of FIGS.  1 - 5 ) beyond the backplane  12  than the header  10  shown in FIGS.  1 - 5 . In addition, a secondary header  10   b  is positioned on the other side of the backplane  12  and generally opposite the primary header  10   a  such that the secondary header  10   b  receives and includes the extended portions of the pairs  24   p  of signal pins  24   a ,  24   b . Accordingly, the backplane  12  is sandwiched between the primary and secondary headers  10   a ,  10   b , each header  10   a ,  10   b  shares the pairs  24   p  of signal pins  24   a ,  24   b  and the ground pins  28 , and a circuit board mounted to the primary header  10   a  is directly interfaced through the backplane  12  to another circuit board mounted to the secondary header  10   b . Each header  10   a ,  10   b  has its own ground shields  26  (the ground shields  26  for the primary header  10   a  are not shown in FIG. 7). Unlike the primary header  10   a , the secondary header  10   b  includes a plurality of securing contacts  50 , where each securing contact  50  electrically contacts a respective ground pin  28  and secures such ground pin  28  to such header  10   b . As seen, each securing contact  50  also electrically contacts at least one ground shield  26  within the secondary header  10   b  through bumps  38   b , thereby electrically connecting the contacted ground shield(s)  26  with the contacted ground pin  28 .  
         [0064]    In particular, the primary header  10   a  of FIG. 7 is substantially identical to the header  10  of FIGS.  1 - 5 , except that the pairs  24   p  of signal pins  24   a ,  24   b  and ground pins  28  extend a relatively longer distance as compared with the header  10  of FIGS.  1 - 5  to allow for rear plug-up. For example, in the header  10  of FIGS.  1 - 5 , such pins  24   a ,  24   b ,  28  extend about 4.3 mm through and beyond the backplane  12 , while in the primary header  10   a  of FIG. 7, such pins  24   a ,  24   b ,  28  extend about 19 mm through and beyond the backplane  12 .  
         [0065]    Preferably, each pin  24   a ,  24   b ,  28  is formed such that the distal end thereof (i.e., the end associated with the secondary header  10   b ) is substantially identical to the proximal end thereof (i.e., the end associated with the primary header  10   a ). Accordingly, the secondary header  10   b  is instantiated by way of a second shroud  14  substantially identical to the shroud  14  of the primary header  10   a , where the second shroud  14  is slipped over the distal end of each pin  24   a ,  24   b ,  28  (FIG. 7A) after such pins are inserted through the backplane  12 . As should be understood, the second shroud  14  is then moved toward the backplane  12  until the base  16  of such second shroud  14  is generally parallel to and in contact with such backplane  12 . As viewed from their respective connector sides  20 , then, the primary header  10   a  and the secondary header  10   b  each present substantially the same profile, pin arrangement, and ‘footprint’. In fact, it is preferable that the primary header  10   a  and the secondary header  10   b  each be able to receive the same type of complementary electrical connector in their respective wells. Preferably, the primary edge  23  of the secondary header  10   b  is directly opposite the primary edge  23  of the primary header  10   a , with respect to the backplane  12 .  
         [0066]    As was discussed above, and as similarly shown in FIGS. 2 and 4, each ground pin  28  in the primary header 10   a  includes a generally planar fin  40  that generally resides within the base  16  of the shroud  14  of the primary header  10   a  and that extends generally laterally from the main body of the ground pin  28 . As seen, each fin  40  has generally opposing planar sides such that each ground shield  26  in the primary header  10   a  is electrically contacted by a ground pin  28  at a planar side of the fin  40  of such ground pin  28 . As was also discussed above, each ground pin  28  is preferably inserted into the shroud  14  of the primary header  10   a  such that the fin  40  maintains an interference fit therewith.  
         [0067]    However, and as should be understood, the insertion of each ground pin  28  through the backplane  12  prevents such ground pin  28  from having a second fin on the distal end thereof. Accordingly, and as was discussed above, it is preferable that the secondary header  10   b  include a plurality of securing contacts  50 , where each securing contact  50  contacts a respective ground pin  28 , secures such ground pin  28  to such header  10   b , electrically connects such ground pin  28  to at least one ground shield  26  (through bumps  38   b ), and in effect performs the same function as a fin  40 .  
         [0068]    In particular, it is preferable that, prior to being mounted to the backplane  12  and the pins  24   a ,  24   b ,  28 , the second shroud  14  be fitted with a plurality of conductive securing contacts  50 , where one contact  50  is in each space in the base  16  of the second shroud  14  where a second fin of a ground pin  28  would otherwise reside. The insertion of contacts  50  is generally similar to the insertion of shields  26  into the base  16 . As seen in FIG. 7B, each such securing contact  50  has generally opposing planar sides, and as positioned in the second shroud  14  of the secondary header  10   b  is electrically contacted on at least one side by a ground shield  26  in the secondary header  10   a  at a planar side of such securing contact  50 .  
         [0069]    When the second shroud  14  is slipped over the distal end of each pin  24   a ,  24   b ,  28  and moved toward the backplane  12 , then, each securing contact  50  in such second shroud  14  securingly electrically contacts the side of a respective ground pin  28  and maintains an interference fit therewith. Preferably, each securing contact  50  includes a compliant or spring portion  52  in facing relation to the side of the respective ground pin  28  to assist in securingly electrically contacting the respective ground pin  28  and maintaining the interference fit therewith. As with the fin  40 , each securing contact  50  engages bumps  38   b  on the contacted-to ground shields  26 . However, any other appropriate mechanism may be employed to perform such functions without departing from the spirit and scope of the present invention.  
         [0070]    With such securing contacts  50 , the ground shields  26  in the second shroud  14  are electrically coupled to the ground pins  28 . In addition, the entire second shroud  14  is secured to the backplane  12 . The interference fit between the securing contacts  50  and the ground pins  28  secures the second shroud  14  to the backplane  12 .  
         [0071]    The header  10  and its variations as discussed above have proven to be remarkably capable of reducing noise and/or cross-talk. However, the particular design of such header  10  and its variations may not accommodate parts having relatively large dimensional variations.  
         [0072]    In particular, and as was discussed above, each ground pin  28 , each ground shield  26 , and each signal pin  24   a ,  24   b  is inserted into the base  16  of the shroud  14  and is held in place by an interference fit. Specifically, each ground pin  28  in the interior columns  32   bi  maintains an interference fit between contacted bumps  38   b  on flanking ground shields  26 , each ground pin  28  in the exterior columns  32   be  maintains an interference fit between a bump  38   b  at an adjacent ground shield  26  and with an interior surface of the base  16  (not shown), and each ground shield  26  also includes a bump  38   a  at a surface thereof to assist in maintaining an interference fit of such ground shield  26  directly with the base  16  of the shroud  14 . Of course, each signal pin  24   a ,  24   b  also maintains an interference fit with such base  16 .  
         [0073]    Of particular interest here is the bumps  38   a ,  38   b  on the ground shields  26 , which have heretofore been shown and described as rigid. Being rigid, such bumps  38   a ,  38   b  afford little flexibility and therefore can fail to in fact effectuate the aforementioned interference fits if housing  12 , shields  26 , or pins  24  are not dimensionally precise. That is, if an aperture in the header base  16  is slightly too wide, or if an interfacing bump  38   a ,  38   b  on an inserted ground shield  26  is slightly too short, such rigid bump  38   a ,  38   b  with little if any ‘give’ does not contact its intended contact point within such aperture, does not contact a ground pin  28  (if a bump  38   b ), and does not help to hold the ground shield  26  within the aperture by way of an interference fit. As a result, such ground shield  26  intermittently or entirely out of contact with a ground pin  28  (if a bump  38   b ) may fail to properly electrically shield, and can fall out of the base  16 . Conversely, if an aperture in the header base  16  is slightly too narrow, or if a bump  38   a ,  38   b  on an inserted ground shield  26  is slightly too tall, such bump  38   a ,  38   b  may cause excessive strain within the base  16  which can lead to immediate or eventual structural failure. As a result, the header  10  could be damaged or destroyed.  
         [0074]    The aforementioned predicament is at least partially resolved by converting at least one of the rigid bumps  38   a ,  38   b  into a relatively flexible bump. In particular, and in one embodiment of the present invention, and referring now to FIGS. 8 and 9, a modified ground shield  60  is introduced in place of the ground shield  26  of FIGS.  1 - 7 . Such ground shield  60  is generally planar and extends generally in the first direction (as indicated by the arrow R) along the base  16  and above a corresponding signal pin  24   a ,  24   b , and therefore does not have the wings  36   a ,  36   b  of the ground shield  26 . Accordingly, the fin  40  of the ground pin  28  is relied upon to provide shielding in the second direction (as indicated by the arrow C in FIGS.  1 - 7 ) along the base  16 .  
         [0075]    Importantly, each ground shield  60  contacts a corresponding ground pin  28  by way of a flexible bump  62 , where such flexibility is achieved by placing the bump  62  at a distal end of a cantilevered beam  64  that extends out from the ground shield  60  at a lateral side thereof adjacent a contacted-to ground pin  28 . It is to be appreciated, that mechanisms other than the beam  64  may be employed to impart flexibility to the bump  62  without departing from the spirit and scope of the present invention.  
         [0076]    As may be appreciated from FIGS. 8 and 9, such beam  64  resides in and cantilevers within the general plane of the ground shield  60 . As may also be appreciated, the cantilevered beam  64  is sufficiently flexible so as not to deform permanently within the aperture space provided for the ground shield  60  when such ground shield  60  is inserted thereinto. Nevertheless, the beam  64  is sufficiently rigid so that the bump  62  at the end thereof provides adequate force against the ground shield  60  to maintain an interference fit in the first direction within such aperture space and contact the contacted-to ground pin  28  even if such aperture space is somewhat tight or loose in the first direction. As a result, the ground shield  60  allows for a relatively wide variation in the dimensions of the housing  12 , shield  60  and pins  24  in the first direction in the aperture space within which such ground shield  60  is received. Note that while the cantilevered beam  64  introduces an unshielded gap to the ground shield  60 , such gap is believed to allow merely an insubstantial amount of cross-talk and/or noise to pass therethrough.  
         [0077]    As shown in FIGS. 8 and 9, adjacent ground shields  60  (i.e., those flanking a corresponding ground pin  28  or those between adjacent ground pins  28  in the first direction) are generally complementary or mirror-image in design, especially when additional features of the ground shields  60  (discussed below) on the planar sides of the ground shields  60  are taken into account. Nevertheless, it is believed that generally identical ground shields  60  may be adjacent one another without departing from the spirit and scope of the present invention as long as the bumps  62  thereof are in contact with corresponding ground pins  28 . In such case, adjacent ground shields  60  would not appear to be mirror-images of each other, which although aesthetically suspect is not believed to detract from the functional aspects of the ground shields  60 .  
         [0078]    As also seen in FIGS. 8 and 9, each ground shield  60  has the relatively rigid bump  38   a  of the ground shield  26 . Accordingly, such ground shield  60  does not necessarily maintain an interference fit within the aperture space provided for the ground shield  60  if such aperture space is relatively loose in the second direction. Likewise, such ground shield  60  may exert excessive force within the aperture space provided for the ground shield  60  if such aperture space is relatively tight in the second direction. As a result, the ground shield  60  does not necessarily allow for a relatively high tolerance in the margin of error in the second direction in the aperture space within which such ground shield  60  is received.  
         [0079]    In one embodiment of the present invention, then, and referring now to FIGS. 10 and 11, an additionally modified ground shield  66  is introduced in place of the ground shield  60  of FIGS. 8 and 9. Such ground shield  66  is also generally planar and extends generally in the first direction (as indicated by the arrow R) along the base  16  and above a corresponding signal pin  24   a ,  24   b , and has the bump  62 , cantilevered beam  64 , and interference fit in the first direction of the ground shield  60 .  
         [0080]    Importantly, each ground shield  66  contacts an inner wall of the aperture space within which the ground shield  66  resides by way of a flexible bump  68 , where such flexibility is achieved by placing the bump  68  at a distal end of a cantilevered beam  70  that extends out from the ground shield  60  at a planar side thereof. In fact, the bump  68  need not necessarily be a protrusion or the like on the beam  70 , but may instead merely be the distal tip or end of the beam  70 . It is to be appreciated that mechanisms other than the beam  70  may be employed to impart flexibility to the bump  68  without departing from the spirit and scope of the present invention.  
         [0081]    As may be appreciated from FIGS. 10 and 11, such beam  70  extends outside of and cantilevers away from the general plane of the ground shield  66 . As with the beam  64 , the cantilevered beam  64  is not so flexible as to deform within the aperture space provided for the ground shield  66  when such ground shield  66  is inserted thereinto. Nevertheless, the beam  70  is flexible enough so that the bump  68  at the end thereof allows the ground shield  66  to maintain an interference fit within such aperture space in the second direction and contact the opposing inner walls of the aperture space even if such aperture space is somewhat tight or loose in the second direction. As a result, the ground shield  66  with the bump  68  at the end of the beam  70  allows for a relatively high tolerance in the margin of error in the second direction in the aperture space within which such ground shield  60  is received. Moreover, such ground shield  66  with the bump  62  at the end of the beam  64  also allows for a relatively high tolerance in the margin of error in the first direction in such aperture space.  
         [0082]    As shown in FIGS. 10 and 11, and as with adjacent ground shields  60 , adjacent ground shields  66  (i.e., those flanking a corresponding ground pin  28  or those between adjacent ground pins  28  in the first direction) are generally complementary or mirror-image in design, especially when the bumps  68  and beams thereof are taken into account. Nevertheless, it is believed that generally identical ground shields  66  may be adjacent one another without departing from the spirit and scope of the present invention as long as the bumps  62  thereof are in contact with corresponding ground pins  28  and the bumps  68  thereof each contact one of the opposing inner walls of the aperture space within which the ground shields  66  reside. Once again, in such case, adjacent ground shields  66  would not appear to be mirror-images of each other, which although aesthetically suspect is not believed to detract from the functional aspects of the ground shields  66 .  
         [0083]    In the headers  10  shown in FIGS.  1 - 11 , each ground shield  26 ,  60 ,  66  generally extends through the base  16  between the connector side  20  and the backplane side  22 , and more preferably from about the surface of the connector side  20  to about the surface of the backplane side  22 . Accordingly, each ground shield  26  preferably has a depth that generally corresponds to a thickness of the base  16  of the shroud  14 . Moreover, in such headers  10 , adjacent ground shields  26 ,  60 ,  66  between adjacent ground pins  28  do not actually contact each other. Accordingly, portions of the material forming the base  16  separate such ground shields  26 ,  60 ,  66  from one another, and in doing so provide structurally integrity to such base  16 . However, such portions also define unshielded gaps between the ground shields  26 ,  60 ,  66 , and such gaps may allow noise and cross-talk to pass through.  
         [0084]    In one embodiment of the present invention, then, and referring now to FIGS. 12 and 13, a further modified ground shield  72  is introduced in place of adjacent pairs of ground shields  66  of FIGS. 10 and 11. Such ground shield  72  is also generally planar and extends generally in the first direction (as indicated by the arrow R) along the base  16 . Here, the ground shield  72  is positioned above a corresponding pair  24   p  of signal pins  24   a ,  24   b , and exhibits no gap such as that in connection with ground shields  26 ,  60 ,  66 . Thus, no gap-related noise and cross-talk is experienced. Moreover, and as should be understood, replacing pairs of ground shields with a single ground shield  72  reduces the number of ground shields and the ground shield insertion time during manufacturing of the header  10  approximately in half.  
         [0085]    As may be appreciated from FIG. 12 in particular, at least at the connector side  20  of the base  16 , the aperture that receives the ground shields  72  and ground pins  28  stretches generally continuously between lateral sides (i.e., left to right) of the base  16 . Accordingly, no portion of the material forming such base  16  bridges across such aperture (i.e., top to bottom) and assists in providing structurally integrity to such base  16 . To provide such structural integrity in the present embodiment, then, such aperture does not in fact extend entirely through the housing  12  between the connector side  20  and the backplane side  22 .  
         [0086]    Instead, and as seen in FIG. 13, such aperture extends from the connector side  20  and stops short of the backplane side  22  in regions where the ground shields  72  are inserted. Thus, the portion of the material forming such base  16  that is not removed at the backplane side  22  assists in positioning the shield  72  properly within the housing  12  and in providing structurally integrity to such base  16 . Consistent with the stop-short aperture, then, and as also seen in FIG. 13, each ground shield  72  as inserted also extends from the connector side  20  and stops short of the backplane side  22 . Put another way, each ground shield  72  has a depth that is less than a thickness of the base  16  of the shroud  14 .  
         [0087]    As a result, the ground shield  72  does not shield within the entirety of the base  16  from the connector side  20  to the backplane side  22  thereof, but from the connector side  20  to the stop-short point adjacent the backplane side  22 . As before, such non-shielded areas may allow noise and cross-talk to pass through, although it is presently believed that such pass-through noise and cross-talk is minimal and in any event less than that in connection with the headers  10  of FIGS.  1 - 11 . Moreover, in the case where the base  16  is molded from a suitable insulative material such as a high temperature plastic, the portion of the material forming the base  16  that is not removed at the backplane side  22  as represented within a mold allows plastic to flow relatively freely within such mold. As should be appreciated, this is especially true as compared with a mold for the base  16  of the header  10  of FIGS.  1 - 11 . As should also be appreciated, free flow contributes substantially to avoiding voids and the like within the base  16  as molded within the mold.  
         [0088]    Of course, the shield  72  and aperture therefor may nevertheless extend entirely through the housing without departing from the spirit and scope of the present invention.  
         [0089]    Still referring to FIGS. 12 and 13, it is seen that the ground shield  72  has a pair of laterally arranged bumps  62 , each one at a distal end of a pair of laterally arranged cantilevered beams  64 . Thus, the ground shield  72  is positioned between a pair of adjacent ground pins  28 , electrically contacts each of the pair of adjacent ground pins  28  by way of the bumps  62 , and maintains an interference fit in the aperture space within which the ground shield  72  resides in the first direction by way of such bumps  62 . Likewise, the ground shield  72  contacts an inner wall of the aperture space within which the ground shield  66  resides by way of a pair of laterally arranged bumps  68 , each one at a distal end of a cantilevered beam  70 . Thus, the ground shield  72  maintains an interference fit within the aperture space in the second direction by way of such bumps  68 . As a result, and similar to the ground shield  66 , the bumps  62 ,  68  of the ground shield  72  allow for a relatively high tolerance in the margin of error in the first and second directions in the aperture space within which such ground shield  72  is received.  
         [0090]    As shown in FIGS. 12 and 13, only a single type of ground shield  72  is required for use in connection with the base  16 , since the same type of ground shield may be used throughout. Nevertheless, differing types of ground shields  72  may be placed within the base  16  departing from the spirit and scope of the present invention as long as the bumps  62  thereof are in contact with corresponding ground pins  28  and the bumps  68  thereof each contact one of the opposing inner walls of the aperture space within which the ground shields  66  reside.  
         [0091]    In the ground shield  72  shown in FIGS. 12 and 13, it is to be appreciated that the pair of bumps  68  thereon are redundant. That is, while both bumps  68  contribute to maintaining the interference fit in the second direction, such fit may also be achieved with only one bump  68 . Moreover, it is to be appreciated that the ground shield  72  is positioned in the aperture space within which such ground shield  72  resides in the first direction solely by way of the ground pins  28  on either side thereof. That is, absence of one or both of such ground pins  28  would allow the ground shield  72  to shift in the first direction.  
         [0092]    In one embodiment of the present invention, then, and referring now to FIGS. 14 and 15, a still further modified ground shield  74  is introduced in place of the ground shield  72  of FIGS. 12 and 13. Such ground shield  74  is similar to ground shield  72  except that (1) the pair of bumps  68  have been replaced by a single bump  68 ; and (2) the bottom edge of the ground shield  74  includes a keying and stabilizing feature keyed to a corresponding feature within the aperture.  
         [0093]    In particular, and still referring to FIGS. 14 and 15, it is seen that the pair of bumps  68  and pair of beams  70  on the ground shield  72  have been replaced on the ground shield  74  by a single bump  68  on a distal end of a cantilevered beam  70 . Thus, the ground shield  74  maintains an interference fit within the aperture space in the second direction by way of such single bump  68 . Moreover, the single bump  68  of the ground shield  74  allow for a relatively high tolerance in the margin of error in such second direction. Preferably, the single bump  68  and beam  70  are constructed to provide sufficient interference fit force, especially as compared with the pairs of bumps  68  and beams  70  of the ground shield  72  of FIGS. 12 and 13.  
         [0094]    Also, the bottom or insertion edge  76  of the ground shield  74  includes a keying and stabilizing feature  78  keyed to a complementary feature  80  of the base  16  within the aperture. As shown in FIGS. 14 and 15, the feature  78  on the ground shield  74  defines a recess that matches a protrusion defined by the feature  80  of the base  16 . The complementary features  78 ,  80  may define any appropriate geometry without departing from the spirit and scope of the present invention. Importantly, the complementary features  78 ,  80  associated with the ground shield  74  and base  16  assist in preventing any shifting of the ground shield  74  within the aperture space within which such ground shield  74  resides in the first direction. Thus, the ground shield  74  maintains an interference fit within the aperture space in the first direction by way of the bumps  62 , and also at least partially by way of the features  78 ,  80 . Moreover, the presence of the features  78 ,  80  relieves the bumps  62  and associated beams  64  from having to bear the full brunt of forces that would cause first direction shifting.  
         [0095]    In the ground shield  74  shown in FIGS. 14 and 15, it is to be appreciated that the cantilevered beams  64  extend out and toward the connector side  20  of the base  16  when such ground shield  74  is inserted. If the ground shields  74  and ground pins  28  are both inserted into the base from the connector side  20 , with the ground pins  28  being inserted before the ground shields  74 , the direction of extension of such beams  64  is not believed to be an issue. In particular, the primary force on the beams  64  during insertion originates adjacent the bump  62  thereof and is generally lateral and toward the direction of deflection, and is therefore not potentially injurious to such beams  64 . In contrast, If the ground pins  28  are inserted after the ground shields  74 , the direction of extension of such beams  64  becomes an issue. In particular, the primary force on the beams  64  during insertion originates adjacent the bump  62  thereof and is generally longitudinal and toward the juncture of the beam  64  and the remainder of the shield  74 , and therefore may cause the beam  64  to crumple.  
         [0096]    In one embodiment of the present invention, then, and referring now to FIGS. 16 and 17, a still further modified ground shield  82  is introduced to accommodate the situation where the ground shields  82  and ground pins  28  are both inserted into the base from the connector side  20 , with the ground pins  28  being inserted after the ground shields  82 . As may be appreciated, such ground shield  82  is similar to ground shield  74  except that the cantilevered beams  64  in the ground shield  76  extend out and toward the backplane side  22  of the base  16  when such ground shield  76  is inserted.  
         [0097]    Thus, if the ground shields  82  and ground pins  28  are both inserted into the base from the connector side  20 , with the ground pins  28  being inserted after the ground shields  82 , the direction of extension of the beams  64  of such ground shield  82  are not believed to be an issue. In particular, the primary force on the beams  64  during insertion originates adjacent the bump  62  thereof and is generally lateral and toward the direction of deflection, and is therefore not potentially injurious to such beams  64 .  
         [0098]    Note that the ground shield  82  differs from the ground shield  74  in the design of the main body of the ground shield  82  adjacent the single bump  68  on a distal end of the cantilevered beam  70 . In particular, the single beam  70  is defined in the ground shield  74  by parallel lancing operations originating at the edge of such ground shield  74  that resides at the connector side  20  once inserted into the base  16 , where such lancing operations take place after the ground shield  74  is stamped or otherwise formed in general. In contrast, the single beam  70  is defined in the ground shield  82  by wells  84  on either side thereof that originate when the ground shield  82  is stamped or otherwise formed in general. Thus, the lancing operations are obviated, and the beam  70  in the ground shield  82  is more clearly delineated.  
         [0099]    In the foregoing description, it can be seen that the present invention comprises new and useful ground shield  60 ,  66 ,  72 ,  74 ,  82  for use within a header  10  having multiple differential signal pairs  24   p  in relatively high density, where the ground shield imparts the header with a relatively high tolerance for margins of error in dimensions of parts thereof. It should be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the inventive concepts thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.