Abstract:
The invention relates to a contact pin having longitudinal surfaces bulged to define opposite contact lines extending in longitudinal direction of the contact pin, wherein in cross section of the contact pin the plane through the two opposite contact lines is offset from the cross sectional centre of the contact pin.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to the field of electrical connector assemblies, to a header connector with one or more contact pins and to a contact pin for such header connectors. 
       BACKGROUND 
       [0002]    With the increasing signalling speed required by present-day systems signals transmitted over a conductor become more and more sensitive to coupling and/or cross talk with neighbouring conductors. Such coupling and/or cross talk interaction between conductors is sensitive to the distance between the conductors. Thus, in order to accurately assess and/or control the amount and/or effect of such interaction on a particular conductor at one or more signal frequencies, the relative positions of the conductors are important. 
         [0003]    The geometry of the conductors and their relative position also impacts the impedance of the system and the electric field. To optimize impedance, this impact should be minimized. 
         [0004]    Furthermore, since there are continuing desires for miniaturization there is a need to provide connector designs which allow a compact build. Further concerns are cost reduction for materials and manufacturing. 
       SUMMARY 
       [0005]    In a first aspect, the contact pin of claim  1  is provided. The asymmetric position of the contact lines make it possible to use it in combination with a receptacle contact having a U-shaped cross section, wherein the material of the contact pin is more concentrated between the contact lines and the walls of the U-shaped section. It has been found that pin material at the opposite side of the contact lines does not substantially contribute to signal transfer and therefore negatively affects crosstalk and impedance. Improved signal transfer and signal integrity are obtained without affecting mating stability and required insertion force. 
         [0006]    In a second aspect a header connector according to claim  2  is provided. The header connector comprises at least one contact pin according to claim  1 , typically a plurality of pins arranged in an array or grid of rows and columns. 
         [0007]    Impedance can be further improved by a connector according to claim  3 . 
         [0008]    In a further aspect a connector assembly according to claim  4  is provided with a header connector and a corresponding receptacle connector. The contacts of the receptacle connector and/or the header connector can for instance have opposite terminal ends for mounting on or in a circuit board. Thus, the terminal end can be a “eye-of-the-needle” press fit contacts type or a “surface mount” contact type. The connector assembly may, e.g., be a straight connector, a mezzanine connector, or have an angle between opposite contacts, e.g., a right angle. 
         [0009]    In a connector according to claim  5  the contact pin is substantially surrounded by the U-shaped portion of the receptacle contact. This further reduces cross-talk effects and improves impedance by reducing local distortions of electric field lines, which could otherwise be caused by a portion of the relatively narrow and sharp contact pin protruding from the relatively bulky and rounded-off receptacle contact. 
         [0010]    Signal transfer and integrity can be further improved with a connector assembly according to claim  6 . 
         [0011]    A connector according to claim  7  makes use of differential pair technology, which reduces crosstalk and electromagnetic interference, noise emission and noise acceptance. Moreover, it can achieve a constant and known characteristic impedance, allowing impedance matching techniques important in a high-speed signal transmission line or high quality balanced line and balanced circuit audio signal path. 
         [0012]    Differential pair technology is further optimized in a connector assembly according to claim  8  or  9 . 
         [0013]    Notwithstanding the different orientation of the contact pins and the receptacle contacts in the ground contacts and signal pairs, the contact lines of these contacts are still coplanar in a connector assembly according to claim  11 . This contributes to optimization of the systems impedance. 
         [0014]    A connector assembly according to claim  12  and/or  13  allows easier insertion of contact pins of any cross sectional geometry into a corresponding receptacle contact. 
         [0015]    The contact pins can advantageously be manufactured in a method according to claim  14 , e.g., by punching or stamping. As an alternative, the contact pin may be stamped and the asymmetric bulge may be produced by coining at least a portion of the contact pin in an appropriate shape. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    These and further aspects will hereafter be more fully explained with reference to the drawings showing an embodiment of the invention by way of example. 
           [0017]      FIG. 1 : shows in perspective view an embodiment of a header connector according to the invention; 
           [0018]      FIG. 2 : shows in perspective cross section a connector assembly of a receptacle connector with the header connector of  FIG. 1 ; 
           [0019]      FIG. 3A : shows in perspective view a contact pin of the header connector of  FIG. 1 ; 
           [0020]      FIG. 3B ; shows the contact pin of  FIG. 3A  in front view; 
           [0021]      FIG. 4 : shows a signal pair and a ground pair of the connector assembly of  FIG. 2 ; 
           [0022]      FIG. 5 : shows a configuration of differential pairs of the connector assembly of  FIG. 2 ; 
           [0023]      FIG. 6 : shows in perspective view a detail of the connector assembly of  FIG. 2 ; 
           [0024]      FIG. 7 : shows a detail of an alternative embodiment of a connector assembly according to the invention; 
           [0025]      FIG. 8 : shows in front view two stages of manufacturing of the contact pin of  FIGS. 3A and 3B . 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0026]      FIG. 1  shows a header connector  1  comprising a base plate  2  and two sidewalls  3  reinforced by ribs  4 . The base plate  2  is provided with a grid-like array of columns and rows of contact openings  5  each accommodating a contact pin  6 . A contact pin  6  is shown in more detail in  FIG. 3 . The contact pins  6  comprise a first terminal end  7  extending from a mating surface  8  for cooperation with a receptacle contact described hereinafter, and a second terminal end  9  which in the shown embodiment is an eye-of-the-needle press fit contact for circuit board mounting. Between the two terminal ends  7 ,  9  the contact pin  6  comprises a profiled middle section  10  moulded into the base plate  2 . As shown in more detail in  FIGS. 3A and 3B , the contact pins  6  have two opposite contact faces  11 ,  12  bulging to form contact lines  13 ,  14  indicated by an interrupted line in the drawing of  FIG. 3A . To allow easier insertion of the contact pin  6  into a receptacle the first terminal end  7  comprises a tapered outer end  15  which gradually narrows down. 
         [0027]    In  FIG. 2  the header connector  1  is shown in perspective cross section, while the header connector  1  is in mating contact with a receptacle connector  20 . The receptacle connector  20  comprises a housing with a mating face  21  and openings  22  each allowing access to a cavity  23  accommodating a receptacle contact  24 . The receptacle contacts  24  each comprise two resilient contact beams  25  slightly inclining towards each other in the direction of the openings  21 . The outer ends  26  of the beams  25  close to the opening  21  are curved towards each other to provide a tight resilient grip for an inserted contact pin. The other ends of the beams  25  are bridged by a back  27  to form a U-shaped section  28 . The back  27  extends in a direction opposite to the beams  25  towards a second terminal end  29 . Such receptacle contacts may for instance be manufactured by stamping or punching a blank and bending, possibly also including a coining step. In the embodiment shown in the drawings the terminal end  29  is under right angles with the contact beams  25  and is shaped as an eye-of-the-needle press fit contact for circuit board mounting. This way the receptacle connector  20  and the header connector  1  form a connector assembly  30  for connecting two circuit boards under right angles. In alternative embodiments different angles are conceivable. 
         [0028]      FIG. 4  shows a group of four contact pins  6  inserted in four respective receptacle contacts  24 . In the drawing line A represents the plane through the contact lines  13 ,  14 , whereas line B represents a vertical plane through the center line of the receptacle contact  24 . Plane A through the contact lines  13 ,  14  is located between the vertical center face B of the contact pin  6  and the back  27  of the U-shaped section  28  of the receptacle contact  24 . 
         [0029]    The contact pins  6  have a side face  31  facing the back  27  of the U-shaped section  28  of the receptacle contact  24 . The side face  31  bulges towards the back  27  to form a third contact line  32 . Here the width of the contact beams  25  is about two times larger than the width of the contact pin  6 . 
         [0030]    The contacts  6 ,  24  in  FIG. 4  are arranged to form a differential signal pair  33  and a pair  34  of ground contacts. With the signal pair  33  the backs  27  of the respective receptacle contacts  24  are turned towards each other so the distance between the conductive parts of the contacts  6 ,  24  is minimized. The backs  27  of the respective receptacle contacts  24  of the ground pair  34  are turned away from each other. The orientation of the corresponding contact pins  6  alternates correspondingly, so the face A through the contact lines  13 ,  14  is always between the back  27  and the vertical center face B of the contact pin  6 . The contact pins  6  and the thickness of the back  27  are configured in such a way that the contact lines  13 ,  14  of the signal pairs  33  in a column are always coplanar with the contact lines  13 ,  14  of the ground pairs  34  and the other signal pairs  33 . In each column and row of the connector assembly signal pairs  33  and ground pairs  34  are arranged in an alternating pattern, as shown in  FIG. 5 . This way each signal pair  33  is effectively shielded by surrounding ground pairs  34 . Within the columns the contact lines  13 ,  14  of all contact pins  6  are coplanar, whereas the cross sectional centre of the contact pins  6  is alternatingly at the left side or at the right side from the contact lines  13 ,  14 . 
         [0031]    As shown in  FIG. 6 , each cavity  23  in the receptacle connector  20  is provided with side walls  35 ,  36  with a rib extending in a direction parallel to the longitudinal direction of the cavity  23 . The rib  37  comprises a lead-in portion  38 . The rib  37  serves to establish the position of the contact beams  25  within the cavity  23  and to keep the contact beams  25  separated from the side walls  35 ,  36 . To allow easier insertion of the contact pin  6  the back  27  of the U-shaped section  28  of the receptacle contact  24  comprises an inwardly chamfered edge  39  directed towards the opening  22  in the mating surface  21 . 
         [0032]    To allow easier insertion further, or alternatively, a protruding portion  43  is provided at the side wall of the cavity, as shown in  FIG. 7 . The protruding portion  43  is arranged in front the back  27  of the receptacle contacts  24  towards the receptacle mating surface  21 . The portion  43  comprises an inwardly chamfered edge  45  directed towards the opening  22  in the mating surface  21  and overlapping at least part of the back  27  of the respective receptacle contacts  24 . 
         [0033]      FIG. 8  shows a method for manufacturing a contact pin  6 . The tip of the contact pin  6  is shown in front view. The contact pin  6  can be manufactured by first manufacturing a regular symmetrical pin having the contact lines  13 ,  14  in its vertical center plane. In a next step a portion  40  of the pin can be removed along a cutting plane parallel but offset to the plane A through the contact lines  13 ,  14 . In the drawing of  FIG. 7  the portion  40  is indicated by dotted lines. The opposite side  41  remains intact. This way, the vertical center plane of the contact pin  6  is shifted towards intact side  41  and the plane A through the contact lines  13 ,  14  becomes offset from the new vertical center plane B.