Patent Publication Number: US-2023137194-A1

Title: Contact assembly for an electrical connector

Description:
BACKGROUND OF THE INVENTION 
     The subject matter herein relates generally to electrical connectors. 
     Electrical connectors are typically used to electrically couple various types of electrical devices to transmit signals between the devices. At least some known electrical connectors include a card edge connector having contacts held in a housing for mating with a circuit card plugged into a card slot of the card edge connector. The contacts include signal contacts and ground contacts arranged in one or more rows for mating with contact pads at the edge of the circuit card. The circuit card is plugged into the card slot in a mating direction. The mating ends of the contacts are typically cup shaped having curved ends to prevent mechanical stubbing of the tips of the contacts on the edge of the circuit card as the circuit card is plugged into the card slot. The curved tips create electrical stubs at the ends of the signal contacts, which negatively affect the electrical performance of the electrical connector. 
     Accordingly, there is a need for robust electrical contacts having improved performance. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one embodiment, a contact assembly for an electrical connector is provided and includes an array of contacts including signal contacts and ground contacts. The ground contacts are interspersed with the signal contacts to provide electrical shielding between corresponding signal contacts. Each signal contact includes a signal contact body having a first side, a second side opposite the first side, a first edge between the first and second sides, and a second edge between the first and second sides opposite the first edge. The signal contact body includes a signal mating end and a signal terminating end. Each signal contact includes a mating ball formed at the signal mating end of the signal contact body. The mating ball is generally spherical shaped. The mating ball and the signal contact body are a homogeneous structure. 
     In another embodiment, an electrical connector is provided and includes a housing having a cavity. The housing has a card slot at a mating end of the housing. The card slot is configured to receive a card edge of a circuit card. The electrical connector includes a contact assembly received in the cavity. The contact assembly includes an array of contacts including signal contacts and ground contacts. The ground contacts are interspersed with the signal contacts to provide electrical shielding between corresponding signal contacts. Each signal contact includes a signal contact body having a first side, a second side opposite the first side, a first edge between the first and second sides, and a second edge between the first and second sides opposite the first edge. The signal contact body includes a signal mating end and a signal terminating end, each signal contact includes a mating ball formed at the signal mating end of the signal contact body. The mating ball is generally spherical shaped. The mating ball includes a mating interface configured to engage a corresponding contact pad on a surface of the circuit card. The mating ball and the signal contact body are a homogeneous structure. 
     In a further embodiment, a method of forming a contact for a contact assembly is provided. The method stamps the contact from a metal blank to form a contact body having a first side, a second side opposite the first side, a first edge between the first and second sides, and a second edge between the first and second sides opposite the first edge. The contact body includes a mating end and a terminating end. The method generates an electrical arc and directing the electrical arc at the mating end to form a molted ball at a distal tip of the contact. The method cools the molten ball using a cooling airflow directed across the molten ball to form a mating ball at the distal tip of the contact having a generally spherical shape. The mating ball and the contact body are a homogeneous structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of an electrical connector formed in accordance with one embodiment. 
         FIG.  2    is a perspective view of the contact assembly formed in accordance with one embodiment. 
         FIG.  3    is a side view of the signal contact formed in accordance with one embodiment. 
         FIG.  4    is a top view of the signal contact formed in accordance with one embodiment. 
         FIG.  5    is a side view of the ground contact formed in accordance with one embodiment. 
         FIG.  6    is a top view of the ground contact formed in accordance with one embodiment. 
         FIG.  7    is a schematic view of a system used to manufacture the signal and ground contacts in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG.  1    is a perspective view of an electrical connector  10  formed in accordance with one embodiment. The electrical connector  10  is configured to be mated with a mating electrical connector  30 . In an exemplary embodiment, the electrical connector  10  has a mating end  20 , a cable end  22 , and one or more cables  24  extending from the cable end  22 . The electrical connector  10  includes a housing  26  configured to hold a contact assembly  100 . In an exemplary embodiment, the housing  26  includes a card slot  28  at the mating end  20 . In the illustrated embodiment, the electrical connector  10  is a communication device, such as a serial attached SCSI (SAS) connector. However, the electrical connector  10  may be another type of electrical connector in an alternative embodiment. For example, the electrical connector  10  may define a socket or receptacle connector, such as a card edge socket connector. 
     The mating electrical connector  30  is configured to be mated with the electrical connector  10 . In an exemplary embodiment, the mating electrical connector  30  has a circuit card  32  at a mating end  34  of the mating electrical connector  30 . The circuit card  32  includes mating contacts  36  at a card edge  38  of the circuit card  32 . The mating contacts  36  may be provided at both sides of the circuit card  32 . The connectors  10 ,  30  may be a high-speed connectors that transmit data signals at speeds over 10 gigabits per second (Gbps), such as over 25 Gbps. The connectors  10 ,  30  may be input-output (I/O) connectors. 
       FIG.  2    is a perspective view of the contact assembly  100  formed in accordance with one embodiment. In an exemplary embodiment, the contact assembly  100  includes an upper contact subassembly  102  and a lower contact subassembly  104  coupled to a frame  106 . The frame  106  supports the upper and lower contact subassemblies  102 ,  104 . Optionally, the upper and lower contact subassemblies  102 ,  104  may be identical to each other and inverted 180°. In alternative embodiments, the contact assembly  100  may be provided without the frame  106 , rather having the upper and lower contact assemblies coupled directly to each other without an intervening supporting structure. In other alternative embodiments, the contact assembly  100  may be provided with a single contact subassembly, such as provided without the lower contact subassembly  104 . 
     The description herein may be made specifically to the “upper” contact subassembly  102  with the qualifier “upper” and may be made specifically to the “lower” contact subassembly  104  with the qualifier “lower” or may be made generically to the upper or the lower contact subassemblies  102 ,  104  without use of the qualifiers “upper” or “lower”. 
     The contact assembly  100  includes a leadframe  110  having an array of contacts  112  including signal contacts  114  and ground contacts  116 . The contact assembly  100  includes a contact holder  120  holding the array of contacts  112 . The contact assembly  100  includes cables  122  terminated to the leadframe  110 . The contact assembly  100  includes a ground bus  124  provided to electrically common the ground contacts  116  and the cables  122 . In an alternative embodiment, rather than being a cabled contact assembly, the contact assembly  100  may be configured to be terminated to a circuit board, such as being soldered or press-fit to the circuit board. 
     In an exemplary embodiment, the cables  122  are twin-axial cables. Each cable  122  include a pair of signal conductors  250  arranged in an insulator  252 , shown in more detail in  FIG.  5   . A cable shield  254  surrounds the insulator  252  to provide electrical shielding for the signal conductors  250 . The cable  122  includes one or more drain wires  256  electrically connected to the cable shield  254 . Other types of cables  122  may be used in alternative embodiments, such as coaxial cables. 
     The contact holder  120  is used to hold the contacts  112 , including the signal contacts  114  and the ground contacts  116 . The contact holder  120  is manufactured from a dielectric material to electrically isolate the contacts  112  from each other. In an exemplary embodiment, the contact holder  120  is overmolded over the leadframe  110  to encase portions of the contacts  112  and hold relative positions of the contacts  112 . The contact holder  120  extends between a front  126  and a rear  128 . 
     In an exemplary embodiment, the contacts  112  are arranged in one or more rows. For example, the upper contacts  112  are arranged in an upper row configured to interface with an upper surface of a circuit card, such as the circuit card  32 , and the lower contacts  112  are arranged in a lower row configured to interface with a lower surface of the circuit card  32 . In an exemplary embodiment, the signal contacts  114  are arranged in pairs, such as differential pairs. The ground contacts  116  are interspersed between the signal contacts  114 , such as between the pairs of the signal contacts  114 , to provide electrical shielding between the corresponding signal contacts  114 . 
     With additional reference to  FIG.  3   , which is a side view of the signal contact  114 , and  FIG.  4   , which is a top view of the signal contact  114 , each signal contact  114  includes a signal contact body  150  extending between a signal mating end  152  and a signal terminating end  154 . The contact holder  120  holds the signal contact bodies  150  relative to each other. The contact holder  120  maintains spacing between the signal contacts  114 . The signal mating ends  152  are located forward of the contact holder  120 . The signal terminating ends  154  are located rearward of the contact holder  120 . In an exemplary embodiment, the signal contacts  114  include spring beams  156  at the signal mating ends  152 . The spring beams  156  are deflectable spring beams. The spring beams  156  are configured to be coupled to the circuit card  32 . In an exemplary embodiment, the signal contacts  114  include pads  158  at the signal terminating ends  154 . The pads  158  are configured to be welded or soldered to the signal conductors  250  of the cables  122 . The signal terminating ends  154  may include other connection means in alternative embodiments, such as crimp barrels, insulating displacement features, and the like for electrical connection to the signal conductors  250 . In alternative embodiments, the signal terminating ends  154  may include terminating features for terminating the signal contacts  114  to a circuit board, such as solder tails or press-fit pins. 
     In an exemplary embodiment, the signal contact  114  is a stamped and formed contact. The signal contact body  150  is stamped from a metal sheet or blank. The signal contact body  150  includes a first side  160  and a second side  162  opposite the first side  160 . The signal contact body  150  includes a first edge  164  between the first and second sides  160 ,  162  and a second edge  166  between the first and second sides  160 ,  162 . The second edge  166  is opposite the first edge  164 . In an exemplary embodiment, the signal contact body  150  has a rectangular cross-section. The sides  160 ,  162  may be wider than the edges  164 ,  166 . The edges  164 ,  166  may be the cut edges formed during the stamping process. 
     The signal contact  114  includes a signal mating ball  170  formed at the signal mating end  152 . In an exemplary embodiment, the signal mating ball  170  and the signal contact body  150  are a homogeneous structure. For example, the signal mating ball  170  is integral with the spring beam  156  being a unitary, monolithic structure. In an exemplary embodiment, the signal mating ball  170  is formed from the signal mating end  152 . For example, the end of the spring beam  156  may be heated to a molten state to form a molten ball at the distal end and then cooled to cure and fix the signal mating ball  170  at the distal end of the signal contact  114 . The signal mating ball  170  is not solder applied to the end of the spring beam  156 . Rather, the signal mating ball  170  has the same chemical composition as the signal contact body  150 . As such, the signal mating ball  170  is mechanically, rigidly fixed at the distal end of the signal contact  114 , which allows repeated mating to and unmated from the circuit card  32 . The structural integrity of the signal mating ball  170  at the end of the signal contact  114  is maintained through multiple mating cycles. The integrity of the signal mating ball  170  is not affected by heating, such as during operation or use of the electrical connector  10 . The signal path through the signal mating ball  170  and the spring beam  156  is seamless. The signal path does not transition across dissimilar conductive structures, as would be the case with the use of a solder ball, leading to a robust electrical conductor for signal conduction through the signal contact  114 . 
     The signal mating ball  170  is generally spherical shaped. For example, the signal mating ball  170  has a circular cross section. In an exemplary embodiment, the signal mating ball  170  is enlarged relative to the signal contact body  150 . For example, the signal mating ball  170  has a diameter greater than a width of the first and second sides  160 ,  162  and greater than a width of the first and second edges  164 ,  166 . The mating ball  170  has a transition portion  172  that transitions an exterior of the mating ball  170  to an exterior of the signal contact body  150 . The transition portion  172  may include curved surfaces transitioning to the first side  160 , the second side  162 , the first edge  164 , and the second edge  166 . 
     The signal mating ball  170  has a curved mating interface  180 , such as at a bottom  182  of the signal mating ball  170 . The curved mating interface  180  provides a small surface area (for example, a point) configured to interface with the circuit card  32 . The signal mating ball  170  includes a curved surface  184  between the mating interface  180  at the bottom  182  and a distal tip  186  of the signal contact  114 . The curved surface  184  is a wiping surface configured to engage the circuit card  32  during mating. The curved surface  184  provides a smooth transition interface along the signal mating ball  170  as the circuit card  32  is loaded into the electrical connector  10 . The curved surface  184  prevents mechanical stubbing during mating. The signal mating ball  170  has a short, almost non-existent electrical stub rearward of the mating interface  180 . The short electrical stub enhances electrical performance of the signal contact  114  by reducing effect of resonance of the signals through the signal contact  114 . 
     With additional reference to  FIG.  5   , which is a side view of the ground contact  116 , and  FIG.  6   , which is a top view of the ground contact  116 , each ground contact  116  includes a ground contact body  250  extending between a ground mating end  252  and a ground terminating end  254 . The contact holder  120  holds the ground contact bodies  250  relative to each other and relative to the signal contact bodies  150 . The ground mating ends  252  are located forward of the contact holder  120 . The ground terminating ends  254  are located rearward of the contact holder  120 . In an exemplary embodiment, the ground contacts  116  include spring beams  256  at the ground mating ends  252 . The spring beams  256  are deflectable spring beams. The spring beams  256  are configured to be electrically connected to the circuit card  32 . In an exemplary embodiment, the ground contacts  116  include pads  258  at the ground terminating ends  254 . The pads  258  are configured to be welded or soldered to the drain wires  256  or cable shields  254  of the cables  122  to electrically common the cables  122  and the leadframe  110 . In alternative embodiments, the ground terminating ends  254  may include terminating features for terminating the ground contacts  116  to a circuit board, such as solder tails or press-fit pins. 
     In an exemplary embodiment, the ground contact  116  is a stamped and formed contact. The ground contact body  250  is stamped from a metal sheet or blank, and may be stamped with the signal contact bodies  150  to form the leadframe. The ground contact body  250  may be formed identical to the signal contact body  150 . The ground contact body  250  includes a first side  260  and a second side  262  opposite the first side  260 . The ground contact body  250  includes a first edge  264  between the first and second sides  260 ,  262  and a second edge  266  between the first and second sides  260 ,  262 . The second edge  266  is opposite the first edge  264 . In an exemplary embodiment, the ground contact body  250  has a rectangular cross-section. The sides  260 ,  262  may be wider than the edges  264 ,  266 . The edges  264 ,  266  may be the cut edges formed during the stamping process. 
     The ground contact  116  includes a ground mating ball  270  formed at the ground mating end  252 . The ground mating ball  270  may be formed identical to the signal mating ball  170 . In alternative embodiments, the ground contact  116  may be provided without the ground mating ball  270 . Rather, the distal end of the ground contact  116  may include a cupped or spoon shaped curved mating finger. 
     In an exemplary embodiment, the ground mating ball  270  and the ground contact body  250  are a homogeneous structure. For example, the ground mating ball  270  is integral with the spring beam  256  being a unitary, monolithic structure. In an exemplary embodiment, the ground mating ball  270  is formed from the ground mating end  252 . For example, the end of the spring beam  256  may be heated to a molten state to form a molten ball at the distal end and then cooled to cure and fix the ground mating ball  270  at the distal end of the ground contact  116 . The ground mating ball  270  is not solder applied to the end of the spring beam  256 . Rather, the ground mating ball  270  has the same chemical composition as the ground contact body  250 . As such, the ground mating ball  270  is mechanically, rigidly fixed at the distal end of the ground contact  116 , which allows repeated mating to and unmated from the circuit card  32 . The structural integrity of the ground mating ball  270  at the end of the ground contact  116  is maintained through multiple mating cycles. The integrity of the ground mating ball  270  is not affected by heating, such as during operation or use of the electrical connector  10 . The ground path through the ground mating ball  270  and the spring beam  256  is seamless. The ground path does not transition across dissimilar conductive structures, as would be the case with the use of a solder ball, leading to a robust electrical conductor for ground conduction through the ground contact  116 . 
     The ground mating ball  270  is generally spherical shaped. For example, the ground mating ball  270  has a circular cross section. In an exemplary embodiment, the ground mating ball  270  is enlarged relative to the ground contact body  250 . For example, the ground mating ball  270  has a diameter greater than a width of the first and second sides  260 ,  262  and greater than a width of the first and second edges  264 ,  266 . The mating ball  270  has a transition portion  272  that transitions an exterior of the mating ball  270  to an exterior of the ground contact body  250 . The transition portion  272  may include curved surfaces transitioning to the first side  260 , the second side  262 , the first edge  264 , and the second edge  266 . 
     The ground mating ball  270  has a curved mating interface  280 , such as at a bottom  282  of the ground mating ball  270 . The curved mating interface  280  provides a small surface area (for example, a point) configured to interface with the circuit card  32 . The ground mating ball  270  includes a curved surface  284  between the mating interface  280  at the bottom  282  and a distal tip  286  of the ground contact  116 . The curved surface  284  is a wiping surface configured to engage the circuit card  32  during mating. The curved surface  284  provides a smooth transition interface along the ground mating ball  270  as the circuit card  32  is loaded into the electrical connector  10 . The curved surface  284  prevents mechanical stubbing during mating. The ground mating ball  270  has a short, almost non-existent electrical stub rearward of the mating interface  280 . The short electrical stub enhances electrical performance of the ground contact  116  by reducing effect of resonance of the grounds through the ground contact  116 . 
     With reference back to  FIG.  2   , in an exemplary embodiment, the ground bus  124  electrically commons each of the ground contacts  116  with each other. The drain wires  256 , the cable shields  254 , the ground contacts  116  and the ground bus  124  form a ground structure  258  of the electrical connector  10 . The ground bus  124  is separate and discrete from the leadframe  110 . Both the ground bus  124  and the leadframe  110  are electrically connected to the cable shields  254  of the cables  122  via the drain wires  256  to electrically common the cables  122  and the ground contacts  116 . The ground bus  124  includes ground fingers  200  and a connecting beam  202  between the ground fingers  200 . The ground fingers  200  are aligned with and coupled to the corresponding ground contacts  116 . The connecting beam  202  extends between the ground fingers  200 . The connecting beam  202  mechanically and electrically connects the ground fingers  200 . The ground bus  124  electrically commons each of the ground contacts  116 . 
       FIG.  7    is a schematic view of a system  50  used to manufacture the signal and ground contacts  114 ,  116 . The system  50  includes a stamping machine  52  used to stamp the contacts  114 ,  116  from a metal blank. For example, the array of contacts may be stamped from a single blank as part of a leadframe. The system  50  includes a forming machine  54  used to form the contacts  114 ,  116  into a predetermined shape. The contacts  114 ,  116  may include one or more bends after the forming process, such as to form the spring beams and/or to form the terminating ends relative to the mating ends. Optionally, the stamping machine  52  and the forming machine  54  may be incorporated into a single machine, such as a press machine. 
     The system  50  includes a ball forming machine  60 . The ball forming machine may be integrated with the stamping machine  52  and/or the forming machine  54 . The ball forming machine  60  includes an arc generator  62  for generating an electrical arc. The electrical arc is transmitted into the distal end of the contact to rapidly heat the distal end. In an exemplary embodiment, the arc generator  62  transforms the distal end of the contact into a molten state. The shape of the metal material may change when in the molten state, such as from a rectangular shape to a spherical shape. In an exemplary embodiment, the ball forming machine  60  may include multiple arc generators  62  for generating arcs in multiple contacts simultaneously, such as in all of the contacts of the leadframe. Alternatively, the ball forming machine  60  may include a single arc generator  62  used to form the balls one at a time. The arc generator  62  forms a molten ball at the distal end of the contact. The molten ball is cooled to retain the spherical shape and form a ball at the distal end of the contact (for example, to form the signal mating ball  170  or the ground mating ball  270 ). 
     In an exemplary embodiment, the ball forming machine  60  includes a cooling device  64  used to rapidly cool the molten ball to retain the ball or spherical shape at the distal end of the contact. The cooling device  64  includes a nozzle  66  used to direct the flow of gas (for example, air or other cooling gas) across the molten ball. In an exemplary embodiment, the ball forming machine  60  may include multiple cooling devices  64  and/or multiple nozzles  66  for generating the cooling gas flow for the contacts, such as one for each of the contacts of the leadframe. In alternative embodiments, the ball forming machine  60  may include a single cooling device and/or a single nozzle  66 , which may be used to simultaneously cool all of the contacts or which may cool the contacts one at a time. 
     It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Dimensions, types of materials, orientations of the various components, and the number and positions of the various components described herein are intended to define parameters of certain embodiments, and are by no means limiting and are merely exemplary embodiments. Many other embodiments and modifications within the spirit and scope of the claims will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. § 112(f), unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.