Abstract:
A multipolar plug connector for establishing contact with a multilayer board includes signal contacts that are assigned a first and at least one second screen contact element and are arranged adjacent to the signal contact. Recesses are provided at least on the uppermost Layer of the multilayer board which are suitably sized so as to receive and to lead through at least two screen contact elements assigned to neighboring signal contacts.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Applicant claims priority under 35 U.S.C. §119 of German Application No. 10 2009 004 684.4 filed on Jan. 12, 2009. 
     The present invention relates to a multipolar plug connector for establishing contact with a multilayer board as defined in the preamble of the independent claim. 
     PRIOR ART 
     DE 699 15 882 T2 describes a plug connector suited for high-frequency data transmission. Each signal contact element is assigned a screen or mass contact element. The orientation of the contact elements is selected so as to allow impedance matching. 
     U.S. Pat. No. 6,976,886 B2 describes a plug connector by which a high screening effect between the signal lines one relative to the other, and of the plug connector generally is to be achieved, by a special arrangement and/or orientation of the signal and screen contact elements one relative to the other. The known plug connector is especially well suited for high-frequency signals, and in addition the arrangement of the signal and mass contact elements is especially defined so that a specific surge impedance is provided. 
     The multipolar high-frequency plug connection described by DE 39 36 466 A1 comprises a plug connector having a metallic screen that is connected with two contact elements intended for contact-making with a circuit board. The two mass contact elements are arranged on both outer surfaces of the plug connector. The screen is not especially assigned to a selected signal contact element. 
     DE 29 49 013 A2 describes a frequency-optimized connector between a coaxial cable and a circuit board. The neutral conductor of one coaxial cable is connected with a strip conductor arranged on a board. Screening of the coaxial cable results in a mass surface which, in the area of the signal strip conductor, is subdivided into two mass conductor strips arranged adjacent to the signal conductor strip. At the other end of the board, a multipolar plug connector is fixed on the board by soldering. A plug connector contact element is soldered to the signal strip conductors. At the side of the signal contact element four neighboring contact elements are soldered to the mass surface of the strip conductor arrangement. 
     DE 39 04 461 C1 and DE 39 36 466 A1 describe multipolar high-frequency plug connectors where at least one of the corresponding plug connectors comprises a metallic screen connected with two contact elements intended for establishing contact with a circuit board. The two mass contact elements are arranged on both outer surfaces of the plug connector. 
     DE 198 07 713 A1 describes a plug connector comprising a large number of contact elements. The known plug connector is intended to establish plug connections between backplanes and plug-in cards of what is known as compact PCI systems. 
     Now, it is the object of the present invention to provide a plug connector for establishing contact with a multilayer board, in combination with a multilayer board, which together allow efficient screening up to the upper high frequency range. 
     This object is achieved by the features defined in the independent claim. 
     DISCLOSURE OF THE INVENTION 
     The multipolar plug connector for establishing contact with a multilayer board, which comprises signal contacts that are assigned a first and at least one second screen contact element and are arranged adjacent to the signal contact, distinguishes itself by the fact that recesses are provided at least on the upper layer of the multilayer board which are suitably sized so as to receive and lead through at least two screen contact elements assigned to neighboring signal contacts. 
     It was found by simulation that distributing the screening to at least two screen contact elements assigned to one signal contact considerably improves the screen rate compared with a single screen contact element. In order to adapt the multilayer board to a plug connector, the multilayer board is provided with through-holes that are properly sized to receive and to lead through the at least two screen contact elements. 
     Further, by assigning at least two screen contact elements to each of the signal contacts, uniform local inductivity is achieved within the plug connector, and within the multilayer board as well. Correspondingly, the characteristic or surge impedance is homogeneously distributed within the plug connector and within the multilayer board. 
     Due to that arrangement, the plug connector, in combination with the multilayer board equipped with the plug connector, is generally suited for carrying signal frequencies up to the upper GHz range. The simulation results could be confirmed by experiments. 
     Advantageous embodiments and further developments of the plug connector according to invention for establishing contact to a multilayer board, in combination with an especially designed multilayer board, are apparent from the dependent claims. 
     One embodiment provides that the signal contact which is screened by at least two screen contact elements comprises a pair of signal contact elements which, according to a further development of that embodiment, are suitably connected for carrying differential signals. 
     Another embodiment provides that an electrically conductive screening ring is provided at least in the area of the rear outlet of the contact elements from the plug connector housing, which ring encloses, at least in part, the signal contact to be screened. That feature is suitable to improve the screening effect especially when the screening ring is in contact with the first and the second screen contact element, as provided by a further development of that embodiment. According to another further development of that embodiment, a plurality of screening rings may be connected one with the other. 
     One embodiment provides that the screen contact elements assigned to one signal contact, as well the at least one signal contact element of the signal contact, are arranged one beside the other in a row and/or a column of the plug connector, at least approximately. The uniform geometric arrangement increases the homogeneity of the surge impedance within the plug connector, including the multilayer board equipped with the plug connector. 
     According to another embodiment, the screen contact elements are in contact with mass surfaces provided on one or more layers of the multilayer board, in which case the mass surfaces may be subdivided into a plurality of partial areas in order to influence the screening effect and/or the surge impedance as required. 
     A preferred use of the plug connector with the multilayer board provided for contact-making provides for the use of the multilayer board as a backplane. Details in this respect can be derived from the cited prior art as known from DE 198 07 713 A1. 
     A further development provides that the plug connector is assembled from segments that contain the signal contacts and screen contact elements arranged in a row or column one beside the other. The different segments may comprise a screening sheet at least on one side. Those features allow easy production of the plug connector. 
     Another further development provides that the multilayer board comprises at least a single continuous recess intended to receive and to lead through a pair of signal contact elements. Production of the multilayer board is rendered especially easy if instead of certain individual recesses intended to receive and to lead through each pair of signal contact elements, such receiving and lead-through recesses are provided for every pair of signal contact elements. 
     Other advantageous further developments and embodiments of the plug connector provided for establishing contact with the multilayer board, including the multilayer board, may be derived from the embodiments described in the following, and from the drawings. 
    
    
     
       SHORT DESCRIPTION OF THE DRAWING 
         FIG. 1  shows a three-dimensional representation of a plug connector showing especially a view of the contact-making ends of the contact element; 
         FIG. 2  shows a three-dimensional view of a corresponding plug connector, likewise providing a view of the contact-making ends of the contact elements; 
         FIG. 3  shows a detail of the representation of  FIG. 2 ; 
         FIG. 4  shows a greatly enlarged detail of the representation of  FIG. 2 ; 
         FIG. 5  shows a segment of the plug connector shown in  FIG. 1 ; 
         FIG. 6  shows an isometric diagrammatic representation of a multilayer board with a first configuration of recesses for contact elements; and 
         FIG. 7  shows an isometric diagrammatic representation of a multilayer board with a second configuration of recesses for contact elements. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  shows a three-dimensional representation of a multipolar plug connector  10   a , providing a view especially of the rear ends of contact elements intended for making contact with a multilayer board not shown in  FIG. 1 . A first signal contact  11   a  and a neighboring signal contact  12   a  are arranged in one row or column, by way of example. One signal contact may comprise one or more signal contact elements. Contact between the multipolar plug connector  10   a  and the multilayer board preferably is established by press-in connection. Alternatively, or additionally, soldering may be used. 
     In the illustrated embodiment the first signal contact  11   a  comprises a first and a second signal contact element  13   a ,  14   a , and the neighboring signal contact  12   a  likewise comprises a first and a second signal contact element  15   a ,  16   a.    
     Accordingly, both signal contacts  11   a ,  12   a  are implemented as pairs of signal contact elements by way of example. 
     At least certain selected signal contacts  11   a ,  12   a  of the plug connector  10 a should be screened. Screening is effected by screen contact elements. Instead of assigning one signal contact a single screen contact element only, it is provided to assign the signal contacts a first and at least one second screen contact element. In the illustrated embodiment, the first signal contact  11   a  is assigned a first screen contact element  17   a  and at least one second screen contact element  17   a ′, the first screen contact element  17   a  being arranged on the one side of the signal contact  11   a  and the other screen contact element  17   a ′ being arranged on the other side of the signal contact  11   a , so that the signal contact  11   a  is enclosed by its associated screen contact elements  17   a ,  17   a ′ at least in part. 
     The first screen contact element  18   a  and the at least one second screen contact element  18   a ′ are assigned to the neighboring signal contact  12   a.    
       FIG. 2  shows a plug connector  10   b  corresponding to the plug connector  10   a  shown in  FIG. 1 . While the plug connector  10   a  shown in  FIG. 1  comprises spring contacts, for example, the corresponding plug connector  10   b  shown in  FIG. 2  is equipped with the matching blade contacts. Those parts in  FIG. 2  that correspond to the parts illustrated in  FIG. 1  are indicated by the same reference numerals, with the index “a” replaced by index “b”. That convention will be followed also in the description of the following Figures. 
     The corresponding plug connector  10   b  illustrated in  FIG. 2  shows an embodiment using a screening ring  20  that encloses the signal contacts  11   b ,  12   b  at least in part. The screening ring  20  exists at least in the area of the rear portion of the plug connector  10   b  which is intended to establish contact with the multi-layer board. Additionally or alternatively, the screening ring  20  may also be provided in the inner area of the plug connector  10   b . Of course such a screening ring may also be provided in the plug connector  10   a  configured according to  FIG. 1 . 
       FIG. 3  shows a detail of  FIG. 2  viewed from a different perspective. Especially,  FIG. 3  shows another configuration which provides that the screening ring  20 , enclosing the signal contacts  11   b ,  12   b  at least in part, interconnects the screen contact elements  17   b ,  17   b ′;  18   b ,  18   b ′ associated with the signal contact  11   b ,  12   b . In addition, there can be seen another embodiment which provides that the screen contact elements  17   b ,  17   b ′;  18   b ,  18   b ′ of a plurality of signal contacts  11   b ,  12   b  are interconnected by the screening ring  20 . 
       FIG. 4  shows a greatly enlarged detail of  FIG. 2  in which the screening ring  20  can be seen with particular clarity. In this embodiment, too, the screen contact elements  17   b ,  17   b ′ assigned to one signal contact  11   b  are interconnected in an electrically conductive manner by the screening ring  20 . In addition, that Figure likewise shows the embodiment where the screening ring  20  interconnects the screen contact elements  17   b ,  17   b ′,  18   b  respectively assigned to neighboring signal contacts. 
       FIG. 5  shows one segment  30  of the plug connector  10   a  illustrated in  FIG. 1 . The design by segments allows the plug connector  10   a  to be formed from a plurality of segments  30  arranged in series. This allows the production of the plug connector  10   a  to be considerably facilitated.  FIG. 5  shows a screening sheet  31  which covers all contact elements  13   a ,  13   b ,  14   a ,  14   b ,  15   a ,  15   b ;  16   a ,  16   b ,  17   a ;  17   b ,  17   a ′,  17   b ′;  18   a ,  18   b ,  18   a ′,  18   b ′, thereby screening them from the neighboring corresponding contact elements of the next segment  30 , not shown in the drawing. 
       FIG. 6  shows a first embodiment of a multilayer board  40  comprising a plurality of layers  41 ,  42 ,  43 . The multilayer board  40  is prepared for contact-making with the plug connector  10   b  according to  FIG. 1 , or with the plug connector  10   b  according to  FIG. 2 . Accordingly, those parts that correspond to the parts illustrated in  FIGS. 1 and 2  are again indicated by the same reference numerals. The representation of  FIG. 6  corresponds to a section along the surface of the uppermost layer  41  of the multilayer board  40  with assembled plug connector  10   a ,  10   b.    
     Accordingly, there can be seen in the drawing only those parts of the contact elements  13   a ,  13   b ,  14   a ,  14   b ;  15   a ,  15   b ,  16   a ,  16   b ;  17   a ,  17   a ′,  17   b ′;  18   a ,  18   b ,  18   a ′,  18   b ′ that are located in the multilayer board  40 . The signal contact elements  13   a ,  13   b ,  14   a ,  14   b ;  15   a ,  15   b ,  16   a ,  16   b  are respectively located in the recesses  50 ,  51 ,  52 ,  53 . The screen contact elements  17   a ′,  17   b ′,  18   a ,  18   b , which are assigned to neighboring signal contacts  11   a ,  11   b ;  12   a ,  12   b , are located in a single continuous recess  54 ,  54 ′,  54 ″ according to the invention. 
     The screen contact elements  17   a ,  17   b ,  17   a ′,  17   b ′;  18   a ,  18   b ,  18   a ′,  18   b ′ are preferably in contact with mass surfaces  55 ,  56 ,  57  that may be arranged on different layers  41 ,  42 ,  43  of the multilayer board  40 . Contact is made preferably by a press-in connection in this case as well. Alternatively or additionally, soldering may be applied. The dimensions of the mass surfaces  55 ,  56 ,  57  may vary depending on the particular requirements. For example, the mass surface  55  arranged on the second layer  42 , and the mass surface  56  arranged on the lowermost layer  42  are subdivided into several partial areas. 
     According to one embodiment, the two signal contact elements  13   a , 13   b ,  14   a ,  14   b ;  15   a ,  15   b ,  16   a ,  16   b , which respectively form a signal contact  11   a ,  11   b ;  12   a ,  12   b , are interconnected in the form of differential contact pairs where one signal contact element  13   a ,  13   b ;  15   a ,  15   b  carries a first signal pattern related to a reference potential, while the second signal contact element  14   a ,  14   b ;  16   a ,  16   b  of the signal contact  11   a ,  11   b ;  12   a ,  12   b  carries an inverted signal pattern. For greater clarity, the one signal contact element  13   a ,  13   b ;  15   a ,  15   b  is designated by a plus sign while the other signal contact element  14   a ,  14   b ;  16   a ,  16   b  is designated by a minus sign. 
       FIG. 6  shows a further embodiment according to which the two signal contact elements  13   a ,  13   b ,  14   a ,  14   b ;  15   a ,  15   b ,  16   a ,  16   b  of at least certain individual signal contacts  11   a ,  11   b ;  12   a ,  12   b  are likewise arranged in a continuous recess  58 ,  59 . 
     The recesses  54 ,  54 ′;  54 ″,  58 ,  59  are provided at least in the uppermost layer  41  of the multilayer board  40  and, if required, also in lower layers  42 ,  43 . 
       FIG. 7  shows another embodiment of the multilayer board  40  which likewise comprises a plurality of layers  41 ,  42 ,  43 . For contact-making the multilayer board  40  is provided with an embodiment of the plug connector  10   a ,  10   b  where the signal contact  11   a ,  11   b ;  12   a ,  12   b  comprises only a single signal contact element  60 ,  61  each. The further embodiments may be configured in accordance with the multilayer board  40  shown in  FIG. 6 . 
     In principle it is possible, though with increased production input, to configure the plug connector  10   a ,  10   b  and the multilayer board  40  to be contacted in such a way that part of the signal contact elements  13   a ,  13   b ,  14   a ,  14   b ;  15   a ,  15   b ,  16   a ,  16   b  of the signal contacts  11   a ,  1  l b ;  12   a ,  12   b  contain only a single signal contact element  60 ,  61  while another part of the signal contact elements  11   a ,  11   b ;  12   a ,  12   b  contain pairs of signal contact elements  13   a ,  13   b ,  14   a ,  14   b ;  15   a ,  15   b ,  16   a ,  16   b.