Abstract:
A header for interconnecting electrical components comprises at least one column of conductors interposed between ground planes, wherein the column of conductors comprises at least a first, second and third conductor. The first conductor is a ground line, the second and third conductors are signal lines, and the first conductor is electrically connected to one of the ground planes, wherein the second conductor is positioned in the column in interposed relation between said first and third conductor.

Description:
FIELD OF THE INVENTION 
     The present invention relates to electrical connectors, and more particularly to modular connectors for connecting daughter printed wiring boards to mother printed wiring boards. 
     BACKGROUND OF THE INVENTION 
     In the manufacture of computers and other electronic apparatus, daughter printed wiring boards (PWBs) are commonly connected to mother PWBs by means of modular electrical connectors, typically comprising a receptacle and a header. A daughter card (or PWB) electrically and mechanically connects to a receptacle, which in turn electrically and mechanically connects to a mother card (or backplane). 
     Modular electrical connectors of the type mentioned above are used, for example, to connect a large number of signal wires to a PWB. Consequently, a connector is provided with a number of columns of contact holes with contact pins disposed therein. An exemplary connecter is an 8×12 connector which has 12 columns of 8 contact holes with contact pins disposed therein. 
     As miniaturization becomes more prevalent, the number of signal wires to be connected to a connector increases, but the dimensions of the connector itself must not increase and preferably should even decrease. This results in an increasing number of signal and ground connections in the limited space of the connector. In high-frequency applications, this results in the risk of cross talk in the signal connections. 
     Accordingly, to combat the risk of cross talk due to mutual EMI of the signal connections, electrical connectors are equipped with shielding to attempt to shield each signal from EMI from neighboring and nearby signals. This shielding can be a conventional mechanical shield or an electrical shield in the form of a ground line. With today&#39;s electrical connectors, however, the current state of shielding still leaves great risk for cross talk. It is, therefore, desirable to provide an electrical connector that has enhanced shielding capabilities, yet does not significantly reduce signal density. 
     Stripline configurations, i.e., arrangements in which conductors in parallel in a dielectric are interposed between ground planes, are known in the art. A need exists for a way to use such configurations to reduce cross. 
     SUMMARY OF THE INVENTION 
     A header for interconnecting electrical components is provided. The header comprises at least one column of conductors interposed between ground planes, wherein the column of conductors comprises at least a first, second and third conductor. The first conductor is a ground line, the second and third conductors are signal lines, and the first conductor is electrically connected to one of the ground planes, wherein the second conductor is positioned in the column in interposed relation between said first and third conductor. 
     In alternate embodiments, the header for interconnecting electrical components comprises a plurality of rows and columns of signal lines, wherein at least one column comprises at least one ground line situated between two signal lines so that the ground line is coplanar with the signal lines. 
     A ground plane for providing at least one ground line throughout a header for interconnecting electrical components also is provided. The ground plane comprises at least one substantially vertically-oriented metal shield section for separating signal lines of adjacent columns and at least one substantially horizontally-oriented ground shield, through which a ground line that carries a ground current passes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top view of a preferred embodiment of a header of the present invention. 
     FIG. 2 is a schematic of a conventional column of eight signal lines from an 8×12 header. 
     FIG. 3 is a schematic of a column of signal lines of the present invention for an 8×12 header. 
     FIG. 4 is a cross-sectional side view of the header of FIG.  1 . 
     FIG. 5 is an inverted rear view of the header of FIG.  1 . 
     FIGS. 6 and 7 are the two side isometric views of the ground plane of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A header for connecting a receptacle to a mother printed wiring board (PWB) and having an improved shielding design is provided. A top view of a preferred embodiment of a header of the present invention is shown in FIG.  1 . This preferred header is an 8×12 header, having twelve columns of eight contact holes, in which are disposed contact pins  10 , each of which can carry a signal. It will be understood that the terminology 8×12 is used even though the drawings show 9 rows of contacts since only 8 rows of contacts on the header mate with contacts on the receptacle while one row of contacts on the header is grounded to a metallic shield on the receptacle. Alternatively, the 8 rows may be any number of rows of preferably at least 5 rows. Also, the 12 columns may alternatively be any number of columns which is a multiple of 3. 
     A schematic of a conventional column of signal lines from an 8×12 header is shown in FIG.  2 . The conventional column of FIG. 2 has signal lines  14 , and a vertically-oriented shield  16  separating the columns of signals from each other. This conventional design provides limited protection against cross talk between signal connections. 
     A schematic of a column of signal lines of the present invention is shown in FIG.  3 . From ground line  12 , there are two signal lines generally A and B (generally at  14 ), followed by a ground line C, two more signal lines D and E, followed by a ground line F, and then two more signal lines G and H. In addition, there are substantially vertically-oriented metal shields  22  and  42  adjacent the signal lines  14  and substantially horizontally-oriented metal shields  28  surrounding the ground lines  12 , C and F. This new design provides enhanced protection against cross talk between signal connections. Preferably, these differential pairs of signal lines  14  are used with high speed signals and are offset 180 degrees. As is known in the art, when differential pair signals are offset by 180 degrees, noise in one signal tends to be cancelled by the noise in the other signal. A further explanation of differential pairs is found at pages 267-268 and 319-320 of “High-Speed Digital Design,” by Howard W. Johnson et al. (Prentice Hall, 1993), the contents of which are incorporated herein by reference. 
     Still referring to FIG. 3, parallel shield sections  22  and  42  are positioned to opposed sides of the ground and signal line conductors. A tab  21  is also used to contact the shield  22  to groundspring element  40  which is also in contact with shield section  42 . It will be appreciated that the ground shield sections  22  and  42  will affect the electromagnetic field around each signal line  14  so as to reduce cross talk between adjacent signal lines  14 . It will also be seen that the ground lines as at lines  12 , C, F at  28  are electrically connected to the shield  22  which will have the effect of further affecting the electromagnetic fields surrounding the signal lines  14  so as to still further enhance cross talk reduction. The tab  21  further enhances grounding and cross talk reduction by allowing ground current from shield section  22  to be further distributed to groundspring element  40  and thus other shield sections such as shield section  42 . 
     FIG. 4 shows a cross-sectional side view of the header of FIG.  1 . Shown in FIG. 4, there is a column comprised of a ground line  12 , which mates with a grounding shield (not shown) on the receptacle, signal lines A, B, D, E, G and H (generally at  14 ), and ground lines C and F, which mate with contacts on the receptacle. FIG. 4 also shows the metal shield  20 , which comprises shields sections  22  situated between the columns of signal contact pins  10  at the location of the signal lines  14 . Slots  24  also are present between the metal shield sections  22  where the ground lines  12 , C and F are located. FIG. 4 also shows the plastic housing  30 , comprising the three walls  32 ,  34  and  36 . FIG. 5 shows an inverted rear view of the header of FIG.  1 . 
     The metal shield  20  of the present invention, referred to as a ground plane  20 , is shown in FIGS. 6 and 7 in the two side isometric views. FIGS. 6 and 7 depict the metal shield sections  22 , the slots  24  between the shield sections  22 , and ground shields  28 , through which the signal contact pins  10  (or signal lines  10 ) that carry the ground lines  12 , C and F pass. Preferably, a ground plane  20  is one member. For example, the ground plane  20  alternatively may be described as a metal shield plate having slots  24  and ground shields  28  perpendicularly attached to the plate just above the location of the slots  24 . 
     The metal shield sections  22  are substantially rectangularly-shaped and are substantially vertically-oriented. The ground shields  28  are substantially rectangularly-shaped and are substantially horizontally-oriented. Preferably, the ground shields  28  are oriented at approximately 90 degrees to the metal shield sections  22 . Each ground shield  28  has four rectangularly-shaped corner tabs  29  that are bent (or curved) upward so that the ground planes  20  can be situated around the signal contact pins  10  without causing damage to the pins  10 . Preferably, the ground shields  28  attach to the pins  10 . 
     The header of the present invention is also equipped with spring arms  43  which are situated on housing wall  32 , as depicted in FIGS. 1,  4  and  5 . These spring arms  43  have a mechanical function and a grounding function. The spring arms  43  mechanically receive the connecting receptacle, to which the daughter card connects. The spring arms  43  also provide an electrical link to the grounding signals  12  of each ground plane  20  by abutting each ground plane  20 . As shown in FIG. 6 and 7, each ground plane  20  has a connecting tab  21  which, by way of each tab&#39;s distal end  41 , electrically connects each ground plane  20  to the series of spring arms  43 . In the embodiment of FIG. 1, this 8×12 header preferably has 6 springs, as shown in FIGS. 1 and 5. 
     The header design of the present invention reduces cross talk between signal lines  14  by providing a 2:1 signal line  14  to ground line  12 , C and F ratio. The header of the present invention also has a conventional footprint that allows it to be used as a header for conventional connectors. The slotted design of the ground shields also allows for more plastic to be present than otherwise be present without the slots  24 , as depicted in FIG.  1 . This strengthens the existing electrical insulation provided by the plastic, thereby further reducing the risk of cross talk. It will also be appreciated that the header of the present invention, by making use of ground planes, allows for the use of fewer ground connections to the printed circuit board. Because fewer pins need to be used for grounding, more pins can be used as signal pins, thereby allowing for more signal density. 
     It is to be understood that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Accordingly, changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.