Abstract:
An electrical connector adapted to receive a mating plug utilizes low-profile jack terminal contacts that can flex in their PCB-anchored base portions, which are substantially parallel to the PCB. Any bend in the distal connecting portion or in the intermediate transition portion of each terminal contact is gradual and forms an obtuse angle, thus minimizing stress concentrations. The contacts preferably are arranged in two oppositely facing and interdigitating rows of four contacts each. In one embodiment, the terminal contacts are anchored to the PCB by a contact cradle that constrains the base portion of each terminal contact at two spaced anchoring locations, allowing the base portion to flex therebetween. In another embodiment, the base portions of the terminal contacts are embedded in at least one elastomeric member, which is fitted to the PCB.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation of application Ser. No. 14/594,640, filed Jan. 12, 2015, which is a continuation of application Ser. No. 12/929,726, filed on Feb. 11, 2011, now U.S. Pat. No. 8,931,167, and claims the benefit of application Ser. No. 12/616,905, filed on Nov. 12, 2009, now U.S. Pat. No. 7,909,657, the contents of each of which are hereby incorporated by reference in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to electrical connectors, such as modular jacks and plugs used in communication and data transmission systems. Examples include eight-position eight-contact (8P8C) modular jacks commonly used as Ethernet connectors. 
       BACKGROUND OF THE INVENTION 
       [0003]    Near-end crosstalk (NEXT) in communication and data system connectors is an objectionable noise that results from capacitive and/or inductive coupling among the exposed, closely spaced, parallel conductors (contacts) within the jack and/or the mating plug. Crosstalk in a communication or data transmission system degrades the noise margin of the system, resulting in greater error rates in the information conveyed. Typical solutions for reducing near-end crosstalk apply crosstalk compensation signals to the affected jack conductors at particular locations. See, e.g., U.S. Pat. Nos. 5,997,358; 6,350,158; 7,153,168; and 7,367,849, and U.S. patent application Ser. No. 12/314,613, filed Dec. 12, 2008, all of which are incorporated by reference herein in their entireties. 
         [0004]    The electrical length of a jack conductor—i.e., the distance between its point of contact with the inserted plug conductor and the point where compensation is applied—is a factor that affects the amount of compensation required. A shorter electrical length translates into more effective compensation up to higher frequencies, requiring less crosstalk compensation. The desired electrical length is less than 0.100 in., preferably closer to 0.060 in. However, the constraints of material and conventional jack geometry have kept the minimum electrical length achievable with traditional spring contact arrangements to greater than 0.130 in. In such arrangements, the jack spring contacts typically project away from the jack&#39;s printed circuit board (PCB) at a steep angle, resulting in high stress concentrations at each contact&#39;s rigid proximal anchoring point when deflected by an inserted connector plug. Any contact arrangement that would further shorten the electrical length must achieve the desired normal contact forces throughout the required contact deflection range without yielding or breaking due to excessive localized stresses. Solutions that attempt to achieve shorter electrical length involve rather complex arrangements, such as a movable second PCB, e.g., as disclosed in U.S. Pat. No. 7,153,168, or unusually long contacts that engage forward compensation contacts (see U.S. Pat. No. 6,350,158). 
         [0005]    Crosstalk amplitude generally increases with higher data transmission rates. Network connectors attached to balanced twisted-pair copper cabling are now expected to meet at least Category 6A performance standards, which require crosstalk levels to be at least 34 dB below the level of the incoming signal at 500 MHz (ANSI/TIA-568-C.2). Demands for even higher data transmission rates are rendering some prior art solutions unsuitable for use in modern networks. A need thus has developed for a low-noise, simple and dependable connector for use in modern communications and data transmission systems. 
       SUMMARY OF THE INVENTION 
       [0006]    The invention utilizes low-profile jack contacts that can flex in their base portions, which are substantially parallel to the PCB. Thus, an electrical connector according to the invention comprises a housing having a plurality of walls and a plug-receiving cavity opening on a front side of the housing. A circuit board in the housing has conductive paths, a plurality of compensation coupling contacts, and one or more compensation elements associated with the compensation coupling contacts. A plurality of resilient, elongated terminal contacts are supported by and extend above the circuit board for making electrical connections with respective wire terminals of an inserted mating connector plug. Each of the elongated terminal contacts is associated with a respective compensation coupling contact and comprises a base portion, a connecting portion and a transition portion interconnecting the base portion and the connecting portion. A majority of the length of the base portion is disposed substantially parallel to the circuit board and is supported thereby for flexural movement. The connecting portion, which makes electrical contact with the respective wire terminal of an inserted connector plug, extends obliquely above the circuit board and has a free end. The transition portion is adapted to make electrical contact with its respective compensation coupling contact, which serves as a fulcrum about which the connecting portion pivots when displaced by the respective wire terminal of an inserted connector plug. 
         [0007]    Preferably, any bend in the transition portion or in the connecting portion of each terminal contact is gradual and forms an obtuse angle, thus minimizing stress concentrations. It is also preferred that the transition portion be wider than the connecting portion and the base portion, both of which preferably taper substantially continuously from the transition portion outward. The electrical connector can be configured with any number of terminal contacts arranged in various ways. For example, when the connector is configured with eight terminal contacts, the contacts preferably are arranged in two oppositely facing and interdigitating rows of four contacts each. 
         [0008]    In one embodiment, the base portion of each terminal contact is constrained at two spaced constraining locations and is able to flex therebetween. One of the constraining locations preferably is at the compensation coupling contact. Constraint of the terminal contact preferably is effected by a contact cradle above the base portions of the terminal contacts and attached to the circuit board. The contact cradle has a pair of discrete constraining surfaces for each terminal contact that engage the respective terminal contact at the constraining locations, preferably with an opening between the constraining surfaces. The contact cradle also has an aperture for each terminal contact through which the respective connecting portion extends and is able to move during plug insertion and removal. 
         [0009]    In another embodiment, instead of constraining the base portions of the terminal contacts at discrete locations, the base portion of each terminal contact is embedded in an elastomeric member that is fixed relative to the circuit board. Preferably, a plurality of terminal contacts are embedded in a common elastomeric member that is fixed relative to the circuit board. It is further preferable to have a plurality of terminal contacts embedded in one common elastomeric member that is fixed relative to the circuit board, and an equal number of terminal contacts embedded another common elastomeric member that is fixed relative to the circuit board. Preferably, the elastomeric members lie substantially in the plane of the circuit board. 
         [0010]    A method according to the invention relates to the manner of making the electrical connector of the second embodiment. The method comprises the steps of embedding base portions of a plurality of elongated, resilient terminal contacts in an elastomeric member, leaving free ends of the terminal contacts exposed; fitting the elastomeric member to a circuit board; and installing the circuit board in a connector housing. The embedding step preferably involves arranging the base portions of the terminal contacts parallel to each other. The step of fitting the elastomeric member to the circuit board preferably involves fitting the elastomeric member so that it lies substantially in the plane of the circuit board. Where two sets of terminal contacts are to be separately supported, each set is embedded in a separate elastomeric member, and the two elastomeric members are fitted to the circuit board so that the base portions of all of the terminal contacts are parallel, and the base portions of one set of terminal contacts extend away from the base portions of the other set of terminal contacts, with the free ends of two sets of terminal contacts interdigitating. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Preferred embodiments of the disclosed invention, including the best mode for carrying out the invention, are described in detail below, purely by way of example, with reference to the accompanying drawing, in which: 
           [0012]      FIG. 1  is a front perspective view of a jack incorporating a PCB and contact assembly according to a first embodiment of the invention; 
           [0013]      FIG. 2  is a side elevational view in longitudinal cross-section of the jack of  FIG. 1 , with one part omitted to reveal some features hidden in  FIG. 1 ; 
           [0014]      FIG. 3  is a front perspective view of the jack PCB and contact assembly of the first embodiment; 
           [0015]      FIG. 4  is an exploded perspective view of the assembly of  FIG. 3 ; 
           [0016]      FIG. 5  is a side elevational view in longitudinal cross-section of the assembly of  FIG. 3 ; 
           [0017]      FIG. 6  is a perspective view of a resilient terminal contact used in the assembly of  FIG. 3 , showing relative stress levels during deflection; 
           [0018]      FIG. 7  is a top plan view of a resilient terminal contact used in the assembly of  FIG. 3 ; 
           [0019]      FIG. 8  is a partial front perspective view of a jack PCB and contact assembly according to a second embodiment of the invention; 
           [0020]      FIG. 9  is a front perspective view similar to  FIG. 8 , with one part omitted to reveal some features hidden in  FIG. 8 ; and 
           [0021]      FIG. 10  is a side elevational view in longitudinal cross-section of the assembly of  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    As used in this application, terms such as “front,” “rear,” “side,” “top,” “bottom,” “above,” “below,” “upwardly” and “downwardly” are intended to facilitate the description of the electrical receptacle of the invention, and are not intended to limit the structure of the invention to any particular position or orientation. 
         [0023]      FIGS. 1 and 2  depict a jack that incorporates a first embodiment of a PCB and contact assembly according to the invention. The jack comprises a dielectric housing  10  similar to that disclosed in U.S. Pat. No. 6,994,594, which is incorporated herein by reference in its entirety. The housing has side walls  12 , a top wall  14 , a rear wall  15 , an extended bottom wall  16  and a front-opening plug-receiving cavity  18 . A wiring unit  20  is coupled to the housing  10  and includes a printed circuit board (PCB)  22  supported on bottom wall  16 , with its narrower front portion  23  extending through an opening in rear wall  15  into the jack interior below cavity  18 . Eight wire terminals  24  are mounted on PBC  22  (only four are visible in  FIG. 2  among posts  24   a ). Wire terminals  24  are standard insulation displacement contacts (IDC) to which standard wiring (not shown) can be connected and then secured under a snap-on cover  25 , which appears only in  FIG. 1 . These terminals are electrically connected via conductive traces or paths on the PCB  22  respectively to eight resilient terminal contacts  40 , which are held in place on the PCB in two offset rows of four contacts each by a dielectric contact cradle  30  secured to the PCB by adhesive or other suitable means. The preferred material for terminal contacts  40  is beryllium copper (BeCu). Other suitable high-performance alloys may also be used. 
         [0024]    Referring to  FIGS. 3 and 4 , contact cradle  30  has a profile that matches the narrower front portion  23  of PCB  22 , and includes a semi-cylindrical post  32  on each side that mates with a corresponding semi-cylindrical recess  26  on each side of PCB  22 . Contact cradle  30  has eight short openings or apertures  34  arranged in two offset rows of four apertures each. A terminal contact  40  extends from the circuit board through each aperture  34 , which is dimensioned to allow the terminal contact  40  to move freely during insertion and removal of a mating plug, i.e., without touching the contact cradle. Contact cradle  30  also has eight longer openings  36  arranged in two offset rows of four openings each. These openings are axially aligned with respective apertures  34  and overlie portions of respective terminal contacts  40 . Thus, the terminal contacts  40  are arranged in two interdigitating rows of four contacts each. 
         [0025]    Referring to  FIGS. 5-7 , each terminal contact  40  has a substantially uniform thickness and three portions: a beam-like base portion  42  extending along the PCB; a connecting portion  44  extending obliquely above the PCB through an aperture  34  for making electrical contact with the respective wire terminal of an inserted connector plug; and a transition portion  46  interconnecting the base portion and the connecting portion. Connecting portion  44  is distally curved to form a crest C and an obtuse angle, terminates in a slightly downwardly turned free end  48 , and tapers from a wider section adjacent transition portion  46  toward its narrower free end  48 . Transition portion  46  is gently curved, forming an obtuse angle where it joins connecting portion  44  and base portion  42 . Transition portion  46  also rests on a respective compensation coupling contact  28  of the PCB, where it is constrained against upward movement by an overlying web  38  of the contact cradle between opening  36  and aperture  34 . A majority of the length of the base portion  42  lies substantially parallel to the PCB  22 . The tail end  47  of the base portion is constrained by a shoulder  39  of the contact cradle at the end of opening  36 . Constraining shoulder  39  can be configured to permit limited upward movement of tail end  47  during insertion of a mating plug, or alternatively configured to prevent any upward movement of tail end  47 . The base portion  42  makes electrical contact with a respective wire terminal  24  via the PCB conductive traces or paths in a known manner. See  FIG. 4 , which schematically shows a representative PCB trace  49  extending from one terminal contact  40 . Alternatively, the transition portion  46  can communicate electrically with a respective wire terminal  24  via its respective compensation coupling contact  28  and an associated PCB trace  49 . 
         [0026]    Compensation coupling contact  28  serves as a fulcrum about which the connecting portion  44  of the terminal contact pivots during connector plug insertion and removal. Accordingly, during pivoting motion of the connecting portion  44 , the unconstrained section of the base portion  42  (between web  38  and shoulder  39 ) flexes, thus distributing bending stresses throughout the length of the contact and minimizing stress concentrations. The non-uniform width of the terminal contact  40 , depicted in  FIG. 7 , results in controlled bending and also contributes to proper distribution of bending stresses. Transition portion  46 , which is the widest and overlies fulcrum  28 , flexes the least. Base portion  42  tapers substantially continuously from there to its tail end  47 , which is about half the width of transition portion  46 . Connecting portion  44  tapers substantially continuously from transition portion  46  toward the even narrower free end  48 . Relative stress levels during deflection are depicted in  FIG. 6 : Lighter shading represents higher stress; darker shading represents lower stress. This distribution of stresses allows for proper generation of normal contact force between the mating conductors, while reducing permanent contact set and the potential for contact failure. 
         [0027]    Compensation (e.g., capacitive) elements  50  on or in the PCB (only one representative element  50  is schematically shown in  FIG. 4 ) communicate with respective compensation coupling contacts  28 . The electrical connection between the transition portion  44  and the compensation coupling contact  28  enables the application of a crosstalk compensation signal to the terminal contact  40  at its fulcrum point. This location is a very short distance—on the order of about 0.080 in.—from the crest C of the connecting portion  44 , where the electrical interface (point of contact) forms between the terminal contact  40  and the wire terminal of a fully inserted conductor plug. Accordingly, the amount of compensation required to counteract objectionable crosstalk is minimized, resulting in improved electrical performance. 
         [0028]    The embodiment of  FIGS. 8-10  incorporates a somewhat different contact anchoring system to achieve substantially the same improved electrical performance in a reliable jack connector. In this embodiment, the jack housing  10  is the same as that illustrated in  FIG. 2 ; the wiring unit  20  includes the same wire terminals  24  mounted on a PCB; and the resilient terminal contacts are arranged in two interdigitating rows of four contacts each. However, the PCB  122  does not have a contact cradle attached to it. Instead, the two rows of contacts  140  are fixed relative to the PCB by two elastomeric members  134 ,  136 , which are fitted to the PCB (e.g., bonded) in mating openings  124 ,  126  substantially in the plane of the PCB. The entire length of the connecting portion  144  of each terminal contact is exposed above the PCB. The elastomeric members  134 ,  136  preferably are made of neoprene (poly-chloroprene) having a durometer hardness of about 40 (Shore A). Other synthetic or natural rubber materials would also be suitable. 
         [0029]    As in the first embodiment, the connecting portion  144  of each terminal contact  140  tapers toward its free end  148 , is distally curved to form a crest C and an obtuse angle, and terminates in a slightly downwardly turned free end  148 . The straight base portion  142  is narrower than the transition portion  146  and is embedded in the elastomeric member  134  (or  136 ). The transition portion  146  makes electrical contact with a respective wire terminal  24  via its respective compensation coupling contact  128  and an associated PCB conductive trace or path (not shown) in a known manner. The transition portion  146  of this embodiment has two gentle reverse bends forming obtuse angles. One bend overlies a respective compensation coupling contact  128  on the PCB, which also communicates with a respective compensation element  150  (only one representative element  150  is schematically shown in  FIG. 9 ). As illustrated in  FIG. 10 , the terminal contacts  140  in their relaxed (undeflected) state are spaced from the compensation coupling contacts  128 , and make an electrical connection with those contacts only when the terminal contacts deflect upon insertion of a mating plug. It is also possible to configure the assembly such that the terminal contacts  140  always engage the compensation coupling contacts  128 . 
         [0030]    Assembly of the jack of the second embodiment involves first embedding the terminal contacts  140 , in their proper parallel positions, in the elastomeric members  134 ,  136 , leaving the connecting portions  144  exposed. The elastomeric members are then fitted to the PCB  122  in openings  124 ,  126 . Fitting of the elastomeric members may involve, for example, bonding the elastomeric members to the PCB and/or engaging mating structures (e.g., ribs and grooves) on the elastomeric members and in the openings  124 ,  126 . The assembled PCB is then installed in the jack housing  10 . 
         [0031]    The eight-position eight-contact (8P8C) jacks of the above two embodiments have been chosen as examples that illustrate the principles of the invention. It should be understood by those skilled in the art that the invention can encompass jacks having a different number and/or arrangement of contacts, and that other changes and modifications may be made without departing from the scope of the invention as defined by the appended claims.