Abstract:
An electrical power connector comprises a housing having a mounting interface and a mating interface. The mating interface defines a plurality of receptacles spaced apart in more than one direction. A plurality of electrical contacts is supported by the housing. These electrical contacts define respective mounting ends that are configured to electrically connect with an electrical component at the mounting interface, and opposed mating ends. At least one of the electrical contacts defines a common contact beam disposed within at least a select one of the receptacles. This common contact beam is configured to be electrically connected to a pair of adjacent electrical contacts of a mated electrical connector.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of provisional U.S. Patent Application Ser. No. 61/228,269 filed on Jul. 24, 2009, the disclosure of which is hereby incorporated by reference as if set forth in its entirety herein. 
    
    
     BACKGROUND 
     An electrical connector may include a plurality of leadframe assemblies disposed adjacent to one another in a connector housing. The connector may have a mounting interface that defines a first plane and mating interface that defines a second plane. Where the plane of the mating interface is orthogonal to the plane of the mounting interface, the connector may be referred to as a right-angle connector. Where the plane of the mating interface is parallel to the plane of the mounting interface, the connector may be referred to as a mezzanine connector. 
     Each such leadframe assembly may include a leadframe housing, which may be made of a dielectric material, such as a plastic, for example. A plurality of electrical contacts may extend through the leadframe housing. The contacts may be made of an electrically conductive material. The contacts may be stamped from a sheet of electrically-conductive material to form a leadframe. The leadframe housing may be overmolded onto the leadframe. Such a leadframe assembly may be referred to as an insert-molded leadframe assembly (IMLA). 
     Each contact may have a mating end, which may be a receptacle, blade, or other desirable mating end. Each contact may have a respective mounting end, which may be an eye-of-the-needle type mounting end, or a pin, ball, or other desirable mounting end, or terminate in a fusible mounting element, such as a solder ball, for example. 
     The mating ends of the contacts within a leadframe assembly may form a linear array extending along a first direction. The mating ends of the contacts may be arranged along a common centerline that extends along the first direction. The mounting ends of the contacts may form a linear array extending along a second direction, which may be parallel to the first direction (in the case of a mezzanine connector) or perpendicular to the first direction (in the case of a right angle connector). The mounting ends of the contacts may align along a common centerline that extends along the second direction. 
     Differential signal pairs of electrical contacts may be arranged edge to edge (i.e., edge-coupled) or broadside-to-broadside (i.e., broadside-coupled). Contacts may be arranged in a signal-signal-ground arrangement along either columns or rows. 
     A differential signal pair has a differential impedance between the positive conductor and negative conductor of the differential signal pair. Differential impedance is defined as the impedance existing between two signal conductors of the same differential signal pair, at a particular point along the length of the differential signal pair. It is desirable to control the differential impedance to match the impedance of the electrical device(s) to which the connector is connected. Matching the differential impedance to the impedance of electrical device minimizes signal reflection and/or system resonance that can limit overall system bandwidth. Furthermore, it is desirable to control the differential impedance such that it is substantially constant along the length of the differential signal pair, i.e., such that each differential signal pair has a substantially consistent differential impedance profile. 
     The differential impedance profile can be controlled by the positioning of the signal and ground contacts. Specifically, differential impedance may be determined by the proximity of the signal contact to an adjacent ground contact, and by the gap between edges of signal contacts within a differential signal pair. 
     To maintain acceptable differential impedance control for high bandwidth systems, it is desirable to control the gap between contacts to within a few thousandths of an inch. Gap variations beyond a few thousandths of an inch may cause an unacceptable variation in the impedance profile; however, the acceptable variation is dependent on the speed desired, the error rate acceptable, and other design factors. 
     In addition to conductor placement, differential impedance may be affected by the dielectric properties of material proximate to the conductors. Generally, it is desirable to have materials having very low dielectric constants adjacent and in contact with as much of the conductors as possible. The use of air rather than plastic as a dielectric provides a number of benefits. 
     Additional background may be found in U.S. Pat. No. 7,270,574, U.S. Pat. No. 6,994,569, and U.S. Patent Application Ser. No. 61/141,990, filed Dec. 31, 2008, the disclosure of each of which is incorporated herein by reference. 
     SUMMARY 
     As disclosed herein, an electrical connector may include a plurality of electrical contacts arranged into rows and columns. An edge-coupled differential signal pair of the contacts may provide a first pre-established differential impedance, while a broadside-coupled differential signal pair of the contacts may provide a second pre-established differential impedance, which may be different from the first pre-established differential impedance. Accordingly, a single connector may be designed to provide an 85±10Ω differential impedance when wired for edge-coupled pairs and a 100±10Ω differential impedance when wired for broadside-coupled pairs. 
     As used herein, the term “pre-established differential impedance” refers to a differential impedance that is designed into the connector, as distinct from a differential impedance that exists merely as a fallout of the design. In other words, the connector is designed to provide two specific differential impedances that are known a priori, as distinct from prior art connectors that are designed to provide one pre-established differential impedance, while the other is not designed into the connector, but rather merely a fallout of design. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts an example mezzanine-style electrical connector. 
         FIGS. 2A and 2B  depict partial sectional views of the connector in  FIG. 1  along plane A and shows different differential signal pair designations within an example contact arrangement. 
         FIG. 3  depicts certain structural aspects of a contact arrangement that may be varied to affect differential impedance. 
         FIG. 4  depicts an example contact arrangement with dielectric walls disposed between columns of electrical contacts. 
         FIGS. 5A and 5B  depict rotation of an example contact arrangement to affect differential impedance. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  depicts an example mezzanine-style electrical connector  12 . Such a connector may include a connector housing  14 , which may be made of a dielectric material, such as a plastic. The connector  12  may include a plurality of electrical contacts (shown in  FIGS. 2A and 2B ). Each contact may have a respective mating end  16  and a respective mounting end  18 . The mounting ends may terminate in fusible elements, such as solder balls  20 . Such a connector  12  may be referred to as a ball grid array connector. The arrangement of the mounting ends  18  may define the connector&#39;s “footprint.” 
       FIGS. 2A and 2B  show arrangements of the contacts of connector  12  according to partial sectional views along plane A of connector  12  as indicated by  FIG. 1 .  FIGS. 2A and 2B  also depict different differential signal pair designations  29 ,  31  within an example contact arrangement. As shown, each of the contacts  22  may have a respective edge  24  and a respective broadside  26 , where the broadside of the contact is wider than the edge. First and second contacts  28 ,  30  are positioned edge-to-edge along a first direction as highlighted in  FIG. 2A  by signal pair designation  29 . The first contact  28  may be positioned broadside-to-broadside with a third contact  32  along a second direction that is perpendicular to the first direction as highlighted in  FIG. 2B  by signal pair designation  31 . 
     The first and second contacts  28 ,  30  may define an edge-coupled differential signal pair  29  having a first pre-established differential impedance Z 1 . The first and third contacts  28 ,  32  may define a broadside-coupled differential signal pair  31  having a second pre-established differential impedance Z 2  that is different from the first pre-established differential impedance Z 1 . For example, the first pre-established differential impedance Z 1  may be 85 ohms, while the second pre-established differential impedance is 100 ohms Z 2 . 
     As used herein, a stated differential impedance value refers to the stated value plus or minus 10% tolerance for that value. For example, the stated value “100Ω” refers to 100 Ω±10%, or 90-110Ω. Similarly, the stated value “85Ω” refers to 85 Ω±10%, or 76.5-93.5 Ω. 
       FIG. 3  depicts certain structural aspects of a contact arrangement that may be varied to affect differential impedance. For example, the distance between the adjacent edges  24  of the first and second contacts  28 ,  30  may be varied, as may the distance between the centerlines of adjacent columns  33 ,  35 . Adjacent columns  33 ,  35  refer to the columns of contacts  24  arranged edge to edge in  FIG. 3 . The distance between the adjacent edges of the first and second contacts may be referred to as the “gap width” shown as “g” in  FIG. 3 . Adjusting the gap width g may affect the distance between the adjacent edges  24  of the first and second contacts  28 ,  30 . The distance between the centerlines of adjacent columns may be referred to as the “column pitch” shown as “p” in  FIG. 3 . Adjusting the column pitch may affect the distance between the adjacent broadsides  26  of the first and third contacts  28 ,  32 . 
     The gap width g and column pitch p may be chosen such that the first and second electrical contacts  28 ,  30  provide the first pre-established differential impedance Z 1 , while the first and third electrical contacts  28 ,  32  provide the second pre-established differential impedance Z 2 . In other words, the connector may be designed to have a gap width g and column pitch p that cooperate to provide two pre-established differential impedances Z 1 , Z 2  in a single connector. That is, the first and second electrical contacts  28 ,  30  may be separated by a first distance along the first direction, and the first and third electrical contacts  28 ,  32  may be separated by a second distance along the second direction, such that the first and second electrical contacts  28 ,  32  provide a first pre-established differential impedance Z 1  and the first and third contacts provide a second pre-established differential impedance Z 2 . Thus, the contacts may be positioned relative to one another such that the first and second pre-established differential impedances Z 1 , Z 2  provided are provided as a result of the arrangement. 
     It should be understood that a contact arrangement such as shown herein may include both edge-coupled and broadside-coupled differential signal pairs  29 ,  31 . Thus, the same connector  12  may simultaneously provide both of two pre-established differential impedances Z 1 , Z 2 . 
     As shown in  FIG. 4 , a dielectric material  34 , such as a plastic, for example, may be disposed between the broadsides of adjacent contacts. The dielectric material  34  may be a dielectric wall disposed between adjacent contact columns  33 ,  35 . 
     As shown in  FIGS. 5A and 5B , such a connector  12  may be mounted onto a substrate  36 . By way of example, the substrate  36  may be a printed circuit board and the connector  12  may be mounted in any of a plurality of orientations. Such a substrate  36  may have an arrangement electrically conductive elements  38 , such as pads or through-holes. The electrically conductive elements  38  may be arranged in an arrangement corresponding to the connector footprint, such that, when the connector  12  is mounted onto the substrate  36 , mounting ends of the contacts  22  may make electrical contact with the electrically conductive elements on the substrate. 
     The substrate  36  may be wired such that a certain two of the electrically conductive elements  38  form a differential signal pair. A connector  12  having a square grid footprint (of solder balls or compliant terminal ends, for example), may be set on the substrate  36  in a first orientation, as shown in  FIG. 5A , or in a second orientation, as shown in FIG.  5 B, that is rotated 90° relative to the first orientation. It should be understood that, when the connector  12  is mounted as shown in  FIG. 5A , the connector  12  will provide the first differential impedance Z 1 , and, when the connector  12  is mounted as shown in  FIG. 5B , the connector  12  will provide the second differential impedance Z 2 . Accordingly, the same connector  12  can provide a selected one of at least two different, pre-established differential impedances Z 1 , Z 2 , on the same substrate  36 , depending on how it is oriented on the substrate. This is advantageous because a single part is capable of producing two distinct impedances. 
     As described above, an electrical connector  12  may be provided by pre-establishing two desired differential impedances Z 1 , Z 2 , and then designing the connector  12  such that an edge-coupled differential signal pair  29  provides the first of the two differential impedances Z 1 , while a broadside-coupled differential signal pair  31  in the same connector  12  provides the second of the two differential impedances Z 2 . 
     In an example embodiment, the contacts  22  may be arranged in a square grid, with a column pitch of 1.4 mm and row pitch of 1.4 mm. The contacts may be 0.35 mm thick (i.e., have 0.35 mm edges) and 1.0 mm wide (i.e., have 1.0 mm broadsides). Thus, the gap width between adjacent contacts in a column maybe 0.4 mm, and the distance between broadsides of adjacent contacts in a row may be 1.05 mm. A dielectric material having a thickness of 0.8 mm may be disposed between the columns, i.e., between the broadsides of adjacent contacts. Thus, the dielectric may be spaced 0.125 mm from the broadsides of the contacts. 
     In such a connector  12 , where the contacts  22  along a column were arranged in a ground-signal-signal-ground arrangement, the differential impedance Z 1  of an edge-coupled differential signal pair  29  was found to be 82-83Ω. In the same connector  12 , where the contacts  22  along a row were arranged in a ground-signal-signal-ground arrangement, the differential impedance Z 2  of a broadside-coupled differential signal pair  31  was found to be 98-99 Ω.