Patent Publication Number: US-2023155328-A1

Title: High-speed electrical connector

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This claims priority to U.S. Patent Application Ser. No. 63/006,960 filed Apr. 8, 2020, the disclosure of which is hereby incorporated by reference as if set forth in its entirety. 
    
    
     BACKGROUND 
     Technical Field 
     This disclosure generally relates to high-speed electrical interconnects, such as RF (radio frequency/single-ended) interconnects and differential signal interconnects. 
     Brief Description of Other Technical Approaches 
     U.S. Pat. Nos. 4,571,014; 5,114,364; 5,197,893; 5,334,050; 5,397,241; 5,507,655; 5,632,634; 5,842,872; 6,464,537; 6,899,566; 7,004,793; 7,048,585; 7,485,001; 7,553,187; 7,927,144; 9,071,001; 10,038,282 and 10,333,237 are hereby incorporated by reference in their entireties. 
     US Patent Publication Nos. 2010/0009571; 2010/0144201 and 2019/0334292 are hereby incorporated by reference in their entireties. 
     ISORATE brand RF jacks and RF cable connectors, all commercially available from SAMTEC, Inc., New Albany, Ind., are hereby incorporated by reference in their entireties. 
     SUMMARY 
     An electrical connector system can include a first electrical signal conductor surrounded on at least three sides by a first shield, a second electrical signal conductor surround on at least three sides by a second shield, and a third shield that surrounds at least three sides of the first shield and at least three sides of the second shield. An electrical connector system can include a first electrical signal conductor surrounded on at least four sides by a first shield, a second electrical signal conductor surround on at least three or at least four sides by a second shield, and a third shield that surrounds at least three sides or at least four sides of the first shield and at least three sides or at least four sides of the second shield. 
     The first electrical signal conductor can include a first conductor mating portion and a first conductor mounting portion. The second electrical signal conductor can include a second conductor mating portion and a second conductor mounting portion. The first shield can include a first shield mounting portion and a first shield mating portion. The second shield can include a second shield mounting portion and a second shield mating portion. A sealing gasket can be positioned between the first shield and the second shield, such as between a butt coupled first shield mating portion and a second shield mating portion. The first shield and the second shield can be at least partially butt coupled at one of their respective ends. A sealing gasket can be positioned where the first shield and the second shield are each butt coupled to one another. The third shield can define a first third shield mating portion and a second third shield mating portion. 
     The first shield can define a first tubular shape. The second shield can define a second tubular shape. The third shield can define a third tubular shape. The third shield can receive, at two opposed ends thereof, the first shield and the second shield. The first electrical signal conductor can define a first length that is surrounded by a combination of the first shield and the third shield. The second electrical signal conductor can define a second length that is surrounded by a combination of the second shield and the third shield. A housing can at least partially surround the first shield and the third shield. A solder charge, such as a first electrical signal conductor SMT attachment attached to the first electrical signal conductor, when reflowed onto a substrate, has a non-spherical cross-sectional shape. 
     Other aspect disclosed herein include a coaxial substrate comprising SMT pads, a method to match impedance that includes a step of reducing pad via stub length, a method to match impedance that includes a step of reducing pad via stub to approximately 0.5 mm to 4 mm, a method to match impedance that include a step of flooding the ground pads of a substrate, and a method to match impedance that includes a step of reducing a width and depth of a solder ball, without reducing or increasing a height of the solder ball. 
     Also included is an electrical connector that includes a single-ended signal conductor, differential signal conductors, or both that is capable of −60 dB or better of unwanted cross-talk through a 75 GHz and/or 0 dB through −3 dB (or better) of insertion loss through 75 GHz. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is perspective view of an electrical connector system including a first electrical connector and a second electrical connector shown mated to the first electrical connector, wherein portions of the first and second electrical connectors are removed for illustration purposes; 
         FIG.  1 B  is a perspective view of the electrical connector system of  FIG.  1 A , showing the first and second electrical connectors including a first electrical shields, respectively; 
         FIG.  1 C  is another perspective view of the electrical connector system of  FIG.  1 B , showing the first and second electrical connectors including a first electrical shields, respectively; 
         FIG.  1 D  is a sectional side elevation view of the electrical connector system of  FIG.  1 B , taken along line  1 D- 1 D; 
         FIG.  1 E  is a perspective view of the electrical connector system of  FIG.  1 B , showing a sealing gasket disposed between the first and second electrical shields; 
         FIG.  1 F  is a perspective view of the electrical connector system of  FIG.  1 B , shown including a third electrical shield; 
         FIG.  1 G  is a sectional side elevation view taken along line  1 G- 1 G of  FIG.  1 F ; 
         FIG.  2 A  is a perspective view of a substrate configured to be mounted to one of the first and second electrical connectors of  FIG.  1 E ; 
         FIG.  2 B  is a perspective view of the substrate of  FIG.  2 A , but showing a mounting substrate mating interface flooded with a ground plane material; 
         FIG.  2 C  is a perspective view of a step of fabricating the substrate illustrated in  FIG.  2 B ; 
         FIG.  2 D  is a perspective view of a further step of fabricating the substrate illustrated in  FIG.  2 B ; 
         FIG.  2 E  is a cross-sectional view of a solder ball of a plurality of solder balls configured to be attached to mounting ends of electrical signal conductors and electrical shields of the first and second electrical connectors of  FIG.  1 E ; 
         FIG.  2 F  is a cross-sectional view of a conventional solder ball; 
         FIG.  2 G  is a chart plotting impedance as a function of time to illustrate the single ended impedance profile of electrical connectors incorporating surface mount technology improvements; 
         FIG.  3    is a perspective view of a plurality of electrical connector systems of  FIG.  1 E ; and 
         FIG.  4 A  is a perspective view of a plurality of electrical connector systems that includes a first single-ended electrical connector mated to a second single-ended electrical connector; and 
         FIG.  4 B  is an enlarged cross-sectional view of a portion of the electrical connector system of  FIG.  4 A , showing a pair of mated electrical signal conductors of the first and second electrical connectors. 
     
    
    
     DETAILED DESCRIPTION 
     Electrical connectors having electrical signal conductors that can be single-ended signal or can differential signal pairs can be, according to S-parameter modeling, capable of transferring data signals at up to 75 GHz, including up to 67 GHz, at cross-talk levels of −60 dB or less, having insertion losses between 0 dB through −3 dB or better. 
     Referring to  FIGS.  1 A- 1 D , an electrical connector system  20  in one example can include a first electrical connector  22  and a second electrical connector  24  configured to mate with each other so as to place the first and second electrical connectors  22  and  24  in electrical communication with each other. The first electrical connector  22  can include a dielectric or electrically insulative first connector housing  26  and at least one first electrical signal conductor  28  such as a pair of first electrical signal conductors  28  supported by the first connector housing  26 . It should be appreciated, of course, that the first electrical connector  22  can include any number of first electrical signal conductors  28  as desired. In one example, the at least one first electrical signal conductor  28  can be insert molded in the first connector housing  26 . Alternatively, the at least one first electrical signal conductor  28  can be stitched into the first connector housing  26 . 
     The second electrical connector  24  can similarly include a dielectric or electrically insulative second connector housing  30  at least one second electrical signal conductor  32  such as a pair of electrical signal conductors  32  supported by second connector housing  30 . the first such as a plurality of second electrical signal conductors. It should be appreciated, of course, that the second electrical connector  24  can include any number of second electrical signal conductors  32  as desired. In one example, the at least one second electrical signal conductor  32  can be insert molded in the second connector housing  30 . Alternatively, the at least one second electrical signal conductor  32  can be stitched into the first connector housing  30 . 
     The first and second electrical connectors  22  and  24  can be mated with each other in respective mating directions that are oriented along a longitudinal direction L. The first and second electrical connectors  22  and  24  can be mated with each other so as to define a separable interface that allows for the first and second electrical connectors  22  and  24  to be unmated with each other without damaging or destroying either of the electrical connectors. Thus, the first and second electrical connectors  22  and  24  can be mated with each other or any other suitable electrical connector after being unmated from each other. The first and second electrical connectors  22  and  24  can be unmated with each other in respective unmating directions that are opposite the mating directions and thus oriented along a longitudinal direction L. 
     When the first and second signal conductors  28  and  32  define respective pairs of signal conductors, the first electrical signal conductors  28  of the pair of first signal conductors  28  can be aligned with each other along a lateral direction A that is perpendicular to the longitudinal direction L. In one example, the first electrical signal conductors  28  of the pair of first signal conductors  28  can define a first differential signal pair. Further, the first electrical signal conductors  28  can be edge coupled. In particular, the first electrical signal conductors  28  define respective opposed edges and respective opposed broadsides in a plane oriented perpendicular to the longitudinal direction that intersects the first electrical signal conductors  28 . The edges can be shorter than the broadsides in the plane. The edges of the first electrical signal conductors  28  can face each other in an edge coupled configuration. Alternatively, the first electrical signal conductors  28  can be broadside coupled wherein the respective broadsides face each other. 
     Further, the second signal conductors  32  of the pair of second signal conductors  32  can be aligned with each other along the lateral direction A. In one example, the second electrical signal conductors  32  of the pair of second signal conductors  32  can define a second differential signal pair. Further, the second electrical signal conductors  32  can be edge coupled. In particular, the second electrical signal conductors  32  define respective opposed edges and respective opposed broadsides in a plane oriented perpendicular to the longitudinal direction that intersects the second electrical signal conductors  32 . The edges can be shorter than the broadsides in the plane. The edges of the second electrical signal conductors  32  can face each other in an edge coupled configuration. Alternatively, the second electrical signal conductors  32  can be broadside coupled wherein the respective broadsides face each other. 
     Whether the first and second signal conductors  28  and  32  define one respective signal conductor ore more than one respective signal conductor, the respective first and second electrical connectors  22  and  24  can define respective widths along the lateral direction A. The first and second electrical connectors  22  and  24  can define respective heights along a transverse direction T that is perpendicular to each of the longitudinal direction L and the lateral direction A. The width of the first electrical connector  22  can be greater than the height of the first electrical connector  22 . Similarly, the width of the second electrical connector  24  can be greater than the height of the second electrical connector  24 . 
     The first signal conductor  28  and the at least one second signal conductor  32  can each be made from copper, a noble metal, a metal alloy, any combination of copper, a noble metal and a metal alloy, or any suitable alternative electrically conductive material. The first signal conductor  28  can define a first conductor mating portion  34   a  (see  FIG.  1 G ), a first conductor mounting portion  34   b  opposite the first conductor mating portion  34   a , and a first intermediate portion  34   c  that extends from the first conductor mating portion  34   a  to the first conductor mounting portion  34   b . In one example, the first signal conductor  28  can be configured as a vertical conductor whereby the first conductor mating portion  34   a  and the first conductor mounting portion  34   b  are aligned with each other along the longitudinal direction L. Alternatively, the first signal conductor  28  can be configured as a right-angle conductor whereby the first conductor mating portion  34   a  and the first conductor mounting portion  34   b  are oriented perpendicular with respect to each other. A first signal conductor solder ball, a first electrical signal conductor solder charge or any other first electrical signal conductor surface mount technology (SMT) attachment  35  (such as a J-lead, a solder pillar commercially available from International Business Machine (IBM) having a place of business in Armonk, N.Y., or the like) can be attached to the first conductor mounting portion  34   b  of the first signal conductor  28 . In one example, the first signal conductor SMT attachment  35  is configured as a solder ball  39 . The at least one first conductor mounting portion  34   b  can have a corresponding at least one first retention portion that intersects the solder ball  39  and retains the solder ball  39  on the corresponding at least one first electrical conductor  28 . 
     Similarly, the second signal conductor  32  can define a second conductor mating portion  36   a , a second conductor mounting portion  36   b  opposite the second conductor mating portion  36   a , and a second intermediate portion  36   c  that extends from the second conductor mating portion  36   a  to the second conductor mounting portion  36   b . In one example, the second signal conductor  32  can be configured as a vertical conductor whereby the second conductor mating portion  36   a  and the second conductor mounting portion  36   b  are aligned with each other along the longitudinal direction L. Alternatively, the second signal conductor  32  can be configured as a right-angle conductor whereby the second conductor mating portion  36   a  and the second conductor mounting portion  36   b  are oriented perpendicular with respect to each other. A second signal conductor solder ball, a second electrical signal conductor solder charge or any other second electrical signal conductor SMT attachment  37  (such as a J-lead, IBM solder pillar, or the like) can be attached to the second conductor mounting portion  36   b  of the second signal conductor  32 . In one example, the second electrical signal conductor SMT attachment  37  is configured as a solder ball  39 . The at least one first conductor mounting portion  34  can have a respective second retention portion that intersects the solder ball  39  and retains the solder ball  39  on the corresponding at least one second electrical conductor  32 . 
     During operation, when the first and second electrical connectors  22  and  24  are mated with each other, the respective first and second mating portions  34   a  and  36   a  define a mating interface, wherein the first and second mating portions  34   a  and  36   a  ride along each other until the first and second electrical connectors  22  and  24  are fully mated with each other. When the first and second electrical connectors  22  and  24  are fully mated, the first and second electrical conductors  34  and  36  are in physical contact with each other and electrical communication with each other, such that electrical signals can be transmitted between the respective first and second electrical conductors  28  and  32 . 
     In one example, the first and second mating portions  34   a  and  36   a  can be hermaphroditic. Further, the first and second mating portions  34   a  and  36   a  can be solid along respective entireties of their respective lengths. In other words, no air gaps exist in the mating portions  34   a  and  36   a  in cross-section along respective planes that are oriented perpendicular to the longitudinal direction L, when the planes travel along the entire respective lengths of the first and second mating portions  34   a  and  36   a . The first conductor mating portion  34   a  can define at least one first beam  38  such as one single first beam  38  shown in  FIG.  1 A  or two first beams  38   a  and  38   b  that are spaced from each other as shown in  FIG.  4 B . The two first beams  38   a  and  38   b  can be spaced from each other along the lateral direction A so as to define a first air gap  41  that can be defined between the at least two first beams  38   a  and  38   b . Similarly, the second conductor mating portion  36   a  can define at least one second beam  40  such as a single second beam  40  as shown in  FIG.  1 A  or two second beams  40   a  and  40   b  as shown in  FIG.  4 B . The two second beams  40   a  and  40   b  can be spaced from each other along the lateral direction A so as to define a second air gap  42  that can be defined between the at least two second beams  40   a  and  40   b.    
     The at least one first beam  38   a  can electrically connect, physically touch, or both with the corresponding at least one second beam  38   b  when the first and second electrical connectors  22  and  24  are mated with each other. In one example, the first mating portions  34   a  and  36   a  can releasably connect to each other when the first and second electrical connectors  22  and  24  are mated with each other, thereby defining a separable mating interface. The electrical signal conductors  28  and  32  illustrated in  FIG.  4 B  can be single ended or can define radiofrequency (RF) conductors, but can alternatively define differential signal conductors as desired as described above with respect to  FIGS.  1 A- 1 D . Alternatively, the electrical conductors  28  and  32  of  FIGS.  1 A- 1 D  can be configured as single-ended or RF conductors as desired. In this regard, the first signal conductors  28  and second signal conductors  32  can define a single-ended configuration, an edge-coupled differential signal pair, a hermaphroditic differential signal pair, a beam-on-beam differential pair, or any combination thereof. The two first signal conductors  28  can be identical to each other, as shown, or may be visually different from one another. For example, one of the two first signal conductors  28  can be a first signal conductor  28  of a first pair of signal conductors, and the other one of the two first signal conductors  28  can be a second signal conductor  28  of the first pair of signal conductors. Similarly, the two second signal conductors  32  can be identical to each other, as shown, or may be visually different from one another. For example, one of the two second signal conductors  32  can be a second signal conductor  32  of a second pair of signal conductors, and the other one of the two second signal conductors  32  can be a second signal conductor  32  of the second pair of signal conductors. 
     With continuing reference to  FIGS.  1 A- 1 D , the first electrical connector  22 , and thus the electrical connector system  20 , can further include a first electrical shield  44 . In one example, the first electrical shield  44  can be electrically conductive. For instance, the first electrical shield  44  can be metallic. Alternatively or additionally, the first electrical shield  44  can include a magnetic absorbing material, such as a lossy material. In some examples, the first electrical shield  44  can be made from copper, a noble metal, a metal alloy, any combination of copper, a noble metal and a metal alloy, electrically conductive carbon or any electrically conductive or magnetic absorbing material. 
     The first shield  44  can be carried or supported by the first connector housing  26 . For instance, the first shield  44  can receive the first connector housing  26 . The first electrical shield  44  can have a first length L 1  along the longitudinal direction L. The at least one first signal conductor  28  can be at least partially surrounded on at least three sides by the first shield  44  along all or any portion of the first length L 1  of the first shield  44 . In one example, the at least one first signal conductor  28  can be surrounded on all sides along all or any portion of first length L 1  of the first shield  44 . Thus, in a plane that is oriented perpendicular to the longitudinal direction L and intersects the at least one first signal conductor  28 , the first shield  44  can define an enclosed first perimeter that fully circumscribes or surrounds the at least one first signal conductor  28  at least at one location along the first length L 1  of the first shield  44 . In some examples, the at least one first signal conductor  28  can be surrounded all sides along an entirety of the first length L 1  of the first shield  44 . The first length L 1  of the first shield  44  can span the intermediate portion  34   c  of the at least one first signal conductor  28 . The first conductor mating portion  34   a  and the first conductor mounting portion  34   b  can extend out with respect to the first shield  44  along the longitudinal direction L. 
     The first shield  44  can be configured as a first sleeve  45  having a first internal surface  43  that defines a first internal void  47  that can extend through an entirety of the first sleeve  45  along the longitudinal direction L. The first shield  44  defines a first external surface  60  that is opposite the first internal surface  43 . The first internal void  47  is sized to accept therein the at least one first signal conductor  28  shown in  FIG.  1 A . In particular, the first internal void  47  can be sized to receive the first connector housing  26  that supports the at least one first signal conductor  28 . The first shield  44  can define a first tubular cross-sectional shape, a square cross-sectional shape having rounded corners, a rectangular cross-sectional shape having rounded corners, a circular cross-sectional shape, a rectangular cross-sectional shape, a square cross-sectional shape, or any suitable alternative cross-sectional shape. 
     The first shield  44  can further include a first relief window  48  that extends through the first sleeve  45  at a location aligned along the transverse direction T with the first conductor mating portion  34   a  of the at least one first electrical conductor  28 . As the first conductor mating portion  34   a  rides along the second conductor mating portion  36   a  during mating of the first and second electrical connectors  22  and  24 , the first conductor mating portion  34   a  can resiliently deflect away from the second conductor mating portion  36   a  along the transverse direction T. The first conductor mating portion  34   a  can deflect toward, and in some instances into, the relief window  48  to prevent the first conductor mating portion  34   a  from contacting the first shield  44  as the first and electrical connectors  22  and  24  are mated with each other. 
     Similarly, the second electrical connector  24 , and thus the electrical connector system  20 , can further include a second electrical shield  46 . In one example, the second electrical shield  46  can be electrically conductive. For instance, the second electrical shield  44  can be metallic. Alternatively or additionally, the second electrical shield  46  can include a magnetic absorbing material, such as a lossy material. In some examples, the second electrical shield  46  can be made from copper, a noble metal, a metal alloy, any combination of copper, a noble metal and a metal alloy, electrically conductive carbon or any electrically conductive or magnetic absorbing material. 
     The second shield  46  can be carried or supported by the second connector housing  30 . For instance, the second shield  46  can receive the second connector housing  30 . The second electrical shield  46  can have a second length L 2  along the longitudinal direction L. The at least one second signal conductor  32  can be at least partially surrounded on at least three sides by the second shield  46  along all or any portion of the second length L 2  of the second shield  46 . In one example, the at least one second signal conductor  32  can be surrounded on all sides along all or any portion of second length L 2  of the second shield  46 . Thus, in a plane that is oriented perpendicular to the longitudinal direction L and intersects the at least one second signal conductor  32 , the second shield  46  can define an enclosed second perimeter that fully circumscribes or surrounds the at least one second signal conductor  32  at least at one location along the second length L 2  of the second shield  46 . In some examples, the at least one second signal conductor  32  can be surrounded all sides along an entirety of the second length L 2  of the second shield  46 . The second length L 2  of the second shield  46  can span the intermediate portion  36   c  of the at least one second signal conductor  32 . The second conductor mating portion  36   a  and the first mounting portion  36   b  can extend out with respect to the second shield  46  along the longitudinal direction L. 
     The second shield  46  can be configured as a second sleeve  49  having a second internal surface  59  that defines a second internal void  51 , and a second external surface  62  opposite the second internal surface  59 . The second internal void  51  can extend through the sleeve  49  along an entirety of the second length L 2 . The second internal void  51  is sized to accept therein the at least one second signal conductor  30  shown in  FIG.  1 A . The second internal void  51  can be sized to receive the second connector housing  30 . The second shield  46  can define a second tubular cross-sectional shape, a square cross-sectional shape having rounded corners, a rectangular cross-sectional shape having rounded corners, a circular cross-sectional shape, a rectangular cross-sectional shape, a square cross-sectional shape, or any suitable alternative cross-sectional shape. 
     The second shield  46  can further include a second relief window  50  that extends through the second sleeve  49  at a location aligned along the transverse direction T with the second conductor mating portion  36   a  of the at least one second electrical conductor  32 . As the second conductor mating portion  36   a  rides along the first conductor mating portion  34   a  during mating of the first and second electrical connectors  22  and  24 , the second conductor mating portion  36   a  can resiliently deflect away from the first conductor mating portion  34   a  along the transverse direction T. Thus, the deflection of the second conductor mating portion  36   a  can be opposite the deflection of the first conductor mating portion  34   a  along the transverse direction T. The second conductor mating portion  36   a  can deflect toward, and in some instances into, the second window  50  to prevent the second conductor mating portion  36   a  from contacting the second shield  46  as the first and electrical connectors  22  and  24  are mated with each other. 
     When the first and second electrical connectors  22  and  24  are mated with each other, the first shield  44  and the second shield  46  can be aligned with each other along the longitudinal direction L. However, in one example, the first and second shields  44  and  46  remain spaced from each other along the longitudinal direction L in their respective entireties. That is, the first electrical shield  44  can define a first shield mounting portion  44   a  and a first shield mating portion  44   b  opposite the first shield mounting portion  44   a  along the longitudinal direction L. Similarly, the second electrical shield  46  can define a second shield mounting portion  46   a  and a second shield mating portion  46   b  opposite the second shield mounting portion  46   a  along the longitudinal direction L. The first and second shield mounting portions  44   a  and  46   a  can face each other and are spaced away from each other along the longitudinal direction L so as to define a gap  53  therebetween. Air can therefore separate immediately adjacent first and second electrical shields  44  and  46  of first and second electrical connectors  22  and  24  that are mated with each other. The first and second shield mounting portions  44   a  and  46   a  can define respective terminal ends of the first and second shields  44  and  46 . The first conductor mating portion  34   a  can extend beyond the first shield mating portion  44   b  of the first shield  44  along the longitudinal direction L. Similarly, the second conductor mating portion  36   a  can extend beyond the second shield mating portion  46   b  of the second shield  46  along the longitudinal direction L. 
     The first shield  44  the second shield  46  can be butt coupled when the first and second electrical connectors  22  and  24  are mated to each other, such that the first shield mating portion  44   b  of the first shield  44  and the second shield mating portion  46   b  of the second shield  46  do not overlap one another as described in more detail below. Stated another way, the first shield  44  is not received within the second shield  46  when the first and second electrical connectors  22  and  24  are mated with each other, and the second shield  46  is not received within the first shield  44  when the first and second electrical connectors  22  and  24  are mated with each other. 
     In one example, the first and second shields  44  and  46  are physically isolated from each other such that they do not physically touch each other when the first and second electrical connectors  22  and  24  are mated with each other. In particular, the first and second shields  44  and  46  can be spaced from each other along the longitudinal direction L. Further, the first and second shields  44  and  46  can be configured such that they do not overlap each other in either the transverse direction T or the lateral direction A. Thus, no plane exists that 1) is oriented in the transverse direction T and the lateral direction A (or perpendicular to the longitudinal direction L), and 2) passes through any respective portions of both the first shield  44  and the second shield  46 . Otherwise stated, a plane that is oriented in the transverse direction T and the lateral direction A (or perpendicular to the longitudinal direction L) and disposed between the first and second mounting portions  44   a  and  46   a  does not pass through any portion of the first electrical shield  44 , and further does not pass through any portion of the second electrical shield  46 . 
     Furthermore, in some examples, the first shield  44  can be the only ground member of the first electrical connector  22 . That is, the first electrical connector  22  does not include any discrete ground conductors. Similarly, in some examples, the second shield  46  can be the only ground member of the second electrical connector  24 . That is, the second electrical connector  24  does not include any discrete ground conductors. Thus, in some example, no grounds of the first electrical connector  22  touch any grounds of the second electrical connector  24  when the first and second electrical connectors  22  and  24  are mated with each other. Otherwise stated, when the first and second electrical connectors  22  and  24  are mated with each other, the first electrical connector  22  has no grounds that are 1) supported directly by the first connector housing  26  and 2) in direct electrical communication with any grounds of the second electrical connector  24  that are supported directly by the second connector housing  30 . The term “direct electrical communication” refers to electrically conductive communication due to direct physical touching. 
     Further, in some examples, the first electrical connector  22  is configured to mate with the second electrical connector  24  along the longitudinal direction, such that no grounds of the first electrical connector  22  overlap with any ground of the second electrical connector  24  in the plane that is oriented perpendicular to the longitudinal direction. Thus, the plane that is oriented perpendicular to the longitudinal direction does not intersect both a ground of the first electrical connector  22  and a ground of the second electrical connector  24 . Further still, in some examples, the first electrical connector  22  has no grounds that are in electrical communication with any grounds of the second electrical connector  24  when the first and second electrical connectors  22  and  24  are mated with each other. 
     As described in more detail below, the electrical connector system  20 , or one of the first and second electrical connectors  22  and  24 , can include a ground member in the form of a third or auxiliary electrical shield  54  (see  FIG.  1 F ) that places the first and second shields  44  and  46  in electrical communication with each other. The first and second shield mating portions  44   b  and  46   b  can be configured to contact the third electrical shield  54  so as to place the first and second electrical shields  44  and  46  in electrical communication with each other. 
     The first electrical connector  22  and the second electrical connector  24  can be hermaphroditic. In particular, the first electrical connector  22  and the second electrical connector  24  can be two visually identical parts, with one of the two visually identical parts rotated 180 degrees about the longitudinal direction L. The first and second electrical shields  44  and  46  can have substantially equal heights in the transverse direction T, substantially equal widths along the lateral direction A, and the first length L 1  can be substantially equal to the second length L 2 . 
     Referring to  FIG.  1 E , the electrical connector system  20  can further include a sealing gasket  52  that is positioned between the first shield  44  and the second shield  46  along the longitudinal direction L. The sealing gasket can be disposed in the gap  53 . Thus, the sealing gasket  52  can be positioned where the first shield  44  and the second shield  46  are butt coupled to one another. The sealing gasket  52  can extend from the first shield  44  to the second shield  46 . For instance, the sealing gasket  52  can extend from the first mounting portion  44   a  of the first shield  44  to the second mounting portion  46   a  of the second shield  46 . The sealing gasket  52  can be sandwiched, compressed, or biased between the first shield  44  and the second shield  46 . Further, the sealing gasket  52  can at least partially or fully surround the respective first and second mating portions  34   a  and  36   a  when the electrical connectors  22  and  24  are mated with each other. The sealing gasket  46  can be configured as an elastomeric electromagnetic interference (EMI) gasket in some examples. The sealing gasket  52  can be one or more or any combination of two or more of elastomeric, electrically conductive elastomeric, physically compressible and electrically conductive, electrically conductive, thermally conductive, non-electrically conductive, non-thermally conductive, magnetic absorbing, or the like. The gasket  52  can extend from the first electrical shield  44  to the second electrical shield  46 , or be positioned between the first electrical shield  44  and the second electrical shield  46 , or can be electrically, physically or electrically and physically connected to each of the first electrical shield  44  and the second electrical shield  46 . 
     The gasket  52 , when electrically conductive, can shorten the ground or reference or return path between the first and second electrical shields  44 ,  46 . The gasket  52  can reduce near-end crosstalk (NEXT), far-end crosstalk (FEXT) or both compared one or both of the first and second electrical shields  44 ,  46  being devoid of the gasket  52 . In other examples, the electrical connector system  20  does not include the gasket  52 . When the electrical conductors of the first and second electrical connectors  22  and  24  define differential signal pairs, and the first and second electrical connectors  22  and  22  are retained in an assembly housing  102  (see  FIG.  3   ) that is made from a polymer, such as a liquid crystal polymer (LCP), the simulated FEXT and NEXT each stay below −60 dB at data transfer frequencies through approximately 15 GHz, the simulated FEXT and NEXT each stay below −60 dB at data transfer frequencies up to approximately 15 GHz when the electrical connector system  20  does not include the gasket  52 . In the same gasketless, differential electrical connector systems  20 , but in an assembly housing  102  made from a magnetic absorbing material, simulated FEXT and NEXT each stay below −60 dB at data transfer frequencies through approximately 80 GHz. However, it is recognized that magnetic absorbing material is expensive. A cost-effective electrical connector system  20  can be carried by the housing  102  made from LCP and can included the gasket  52  in the manner described above. Simulated FEXT and NEXT remain below −60 dB at data transfer frequencies through approximately 72 GHz. 
     Referring now to  FIGS.  1 F- 1 G , and as described above, the electrical connector system  20  can further include an auxiliary or third electrical shield  54 . The third electrical shield  54  can be electrically conductive. For instance, the third electrical shield  54  can be metallic. Alternatively or additionally, the third electrical shield  54  can include a magnetic absorbing material, such as a lossy material. In some examples, the third electrical shield  54  can be made from copper, a noble metal, a metal alloy, any combination of copper, a noble metal and a metal alloy, electrically conductive carbon or any electrically conductive or magnetic absorbing material. 
     The third shield  54  can be carried or supported by the each of the first electrical shield  44  and the second electrical shield  46 . The third electrical shield  54  can have a third length L 3  along the longitudinal direction L. The third length L 3  can span a portion of the first electrical shield  44 , a portion of the second electrical shield  46 , and the sealing gasket  52 . The third length L 3  can be greater in length than either one of or both of the first length L 1  or the second length L 2 , or approximately equal in length to the sum of the first length L 1  and second length L 2 . The terms “approximate,” “substantial,” derivatives thereof, and words of similar import used with reference to a direction, size, shape, dimension, or other parameter include the stated direction, size, shape, dimension, or other parameter and a range of +/−10% of the stated direction, size, shape, dimension, or other parameter, such as +/−9% of the stated direction, size, shape, dimension, or other parameter, such as +/−8% of the stated direction, size, shape, dimension, or other parameter, such as +/−7% of the stated direction, size, shape, dimension, or other parameter, such as +/−6% of the stated direction, size, shape, dimension, or other parameter, such as +/−5% of the stated direction, size, shape, dimension, or other parameter, such as +/−4% of the stated direction, size, shape, dimension, or other parameter, such as +/−3% of the stated direction, size, shape, dimension, or other parameter, such as +/−2% of the stated direction, size, shape, dimension, or other parameter, such as +/−1% of the stated direction, size, shape, dimension, or other parameter. 
     In one example, the third electrical shield  54  can contact, either directly or indirectly, each of the first electrical shield  44  and the second electrical shield  46 , and in this regard can place the first electrical shield  44  in electrical communication with the second electrical shield  46 . In one example, the third shield  54  can physically contact each of the first and second shields  44  and  46 , thereby placing the first and second shields  44  and  46  in electrical communication with each other. The third electrical shield  54  can be configured as a third sleeve  56  that defines a third internal void  57  sized to receive therein the first and second electrical shields  44  and  46 . In one example, the third electrical shield  54  can removably receive either or both of the first and second electrical shields  44  and  46  in the third internal void  57 . The third internal void  57  can define a first portion  57   a  configured to receive the first electrical shield  44 , and a second portion  57   b  configured to receive the second electrical shield  46 . Thus, the first and second electrical shields  44  and  46  can be inserted into the third electrical shield  54  in opposite directions that are defined by the longitudinal direction L. The third electrical shield  54  can define a third tubular cross-sectional shape, a square cross-sectional shape having rounded corners, a rectangular cross-sectional shape having rounded corners, a circular cross-sectional shape, a rectangular cross-sectional shape, a square cross-sectional shape, or any suitable alternative cross-sectional shape. 
     The third electrical shield  54  can define a first, third shield mating portion  55   a  that is configured to mate with the first electrical shield  44 , and a second, third shield mating portion  55   b  that is configured to mate with the second electrical shield  46 . In particular, the third sleeve  56  can define a third internal surface  58  that defines the third internal void  57 , and a third external surface  63  opposite the third internal surface  58 . The third internal surface  58  can also define the first and second, third shield mating portions  55   a  and  55   b . The first, third shield mating portion  55   a  can be opposite the second, third shield mating portion  55   b  along the longitudinal direction L. 
     Thus, the first, third shield mating portion  55   a  can receive the first shield  44  such that the first external surface  60  of the first shield  44  is electrically, physically or both electrically and physically connected to the internal surface  58  of the third shield  54 . Similarly, the second, third shield mating portion  55   b  can receive the second shield  46  such that the second external surface  62  of the second shield  46  is electrically, physically or both electrically and physically connected to the internal surface  58  of the third shield  54 . 
     The first and second shields  44  and  46  can be at least partially surrounded on at least three sides by the third shield  54  along all or any portion of the third length L 3  of the third shield  54 . In one example, the first and second shields  44  and  46  can be surrounded on all sides along all or any portion of third length L 3  of the third shield  54 . Thus, in respective planes that are oriented perpendicular to the longitudinal direction L and intersect the first and second shields  44  and  46 , the third shield  54  can define respective third perimeters that fully circumscribe or surround the first and second electrical shields  44  and  46 . In some examples, the first and second shields  44  and  46  can be surrounded all sides by the third shield  54 . Thus, at least a portion up to an entirety of a first conductor length of the at least one first electrical signal conductor  28  along the longitudinal direction L can be surrounded by a combination of the first electrical shield  44  and the third electrical shield  54 . Similarly, at least a portion up to an entirety of a second conductor length of the at least one second electrical signal conductor  32  along the longitudinal direction L can be surrounded by a combination of the second electrical shield  44  and the third electrical shield  54 . 
     In one example, the third shield  54  can include a respective at least one contact member  64  that projects inward toward either or both of the first and second electrical shields  44  and  46 , and is configured to mate either or both of the first and second electrical shields  44  and  46 . The contact member  64  can project inward along a direction that is defined from the third external surface  63  to the third internal surface  58 . The at least one contact member  64  can be disposed at either or both of the first, third shield mating portion  55   a  and the second, third shield mating portion  55   b . The contact member  64  can be configured in any suitable manner as desired. For instance, the contact member  64  can be configured as one or more spring fingers  66  that project inward along from the third internal surface  58 . The spring fingers  66  can be resilient and deflectable. Thus, when the third shield  54  receives the respective at least one of the first and second electrical connectors  22  and  24 , the spring finger  66  can resiliently deflect outward as it contacts the respective at least one of the first and second electrical shields  44  and  46 . The spring finger  66  thus provides a spring force against the respective at least one external surface of the first and second electrical shields  44  and  46  so as to maintain contact when the at least one of the first and second electrical shields  44  and  46  is received by the third shield  54 . The third shield  54  can include any number of spring fingers  66 , such as at least one, at least two, at least three, at least four, or four or more spring fingers  66 . 
     In another example, the third shield  54  can include at least one embossment that projects inward so as to contact a respective one of the first and second electrical shields  44  and  46 . Each embossment  68  can define a projection  70  that extends inward from the third internal surface  58 . Each embossment  68  can define a corresponding recess that extends into the third external surface  63 . Thus, each embossment  68  can be stamped into the third shield  54 . The projections  70  can a friction fit against the respective at least one of the first and second electrical shields  44  and  46 . Accordingly, the embossment  68  can maintain contact against the respective at least one external surface of the first and second electrical shields  44  and  46  so as to maintain contact when the at least one of the first and second electrical shields  44  and  46  is received by the third shield  54 . The third shield  54  can include any number of embossments  68  as desired. 
     In one example, the third shield  54  can include the spring fingers  66  that contact the first external surface  60  of the first electrical shield  44  when the third shield  54  receives the first electrical shield  44  in the first portion  57   a  of the third internal void  57 . The third shield  54  can further include the embossments  68  that contact the second external surface  62  of the second electrical shield  46  when the third shield  54  receives the second electrical shield  46  in the second portion  57   b  of the third internal void  57 . 
     In some examples, the first electrical connector  22  can include the third shield  54  that is attached to the first electrical shield  44 . For instance, the third shield  54  can be welded or the like to the first electrical shield  44 . Thus, the second electrical shield  46  is placed in contact with the third shield  54  when the second electrical connector  24  is mated with the first electrical connector  22 . The third electrical shield  54  can remain coupled to the first electrical shield  44  when the second electrical connector  24  is unmated from the first electrical connector  22 . In this regard, the third electrical shield  54  can be referred to as an auxiliary electrical shield of the first electrical connector  22 . Thus, the first electrical connector  22  can include the first electrical shield  44  and the third electrical shield  54 . Alternatively, the first electrical shield  44  and the third electrical shield  54  can be defined by one single unitary monolithic electrical shield. 
     In other examples, the second electrical connector  24  can include the third shield  54  that is attached to the second electrical shield  46 . For instance, the third shield  54  can be welded or the like to the second electrical shield  46 . In one example, the second electrical shield  46  can include recesses that receive respective ones of the embossments  68  so as to interlock the third electrical shield  54  with the second electrical shield  46 . The first electrical shield  44  is placed in contact with the third shield  54  when the first electrical connector  22  is mated with the second electrical connector  24 . The third electrical shield  54  can remain coupled to the second electrical shield  44  when the first electrical connector  22  is unmated from the second electrical connector  24 . In this regard, the third electrical shield  54  can be referred to as an auxiliary electrical shield of the second electrical connector  24 . Thus, the second electrical connector  24  can include the second electrical shield  46  and the third electrical shield  54 . Alternatively, the second electrical shield  46  and the third electrical shield  54  can be defined by one single unitary monolithic electrical shield. In one example, the first electrical shield  44 , the second electrical shield  46 , and the third electrical shield  54  define all ground members of the electrical connector system  20 . 
     The first and second electrical connectors  22  and  24  can be configured to be mounted to underlying substrates  72  as described in more detail below with reference to  FIG.  2 B . As described above, each of the first electrical conductors  28  can be attached to the respective first electrical signal conductor SMT attachment  35 . Each of the second electrical conductors  32  can be attached to the respective second electrical signal conductor SMT attachment  37 . Further, the first shield mounting portion  44   a  of the first electrical shield  44  can be attached to a respective at least one first shield SMT attachment  74 . For instance, the first electrical shield  44  can be attached to a plurality of first shield SMT attachments  74 . In one example, the first shield mounting portion  44   a  can each define a plurality of first mounting pins that each attach to a corresponding one of the respective first shield SMT attachments  74 . Similarly, the second shield mounting portion  46   a  of the second electrical shield  46  can be attached to a respective at least one second shield SMT attachment  76 . For instance, the second electrical shield  46  can be attached to a plurality of second shield SMT attachments  76 . In one example, the second shield mounting portion  46   a  can carry a plurality of second mounting pins that each attach to a corresponding one of the respective second shield SMT attachments  76 . In one example, the first and second shield SMT attachments  74  and  76  can be configured as solder balls  39 . 
     Referring now to  FIG.  1 B  in particular, the first shield SMT attachments  74  define grounds and can surround either or both of the at least one first electrical signal conductor SMT attachment  35  and the at least one first conductor mounting portion  34   b . In particular, the first shield SMT attachments  74  define respective geometric centers that lie substantially in a first shield SMT center plane that is oriented perpendicular to the longitudinal direction L. When straight lines are drawn that connect adjacent ones of the geometric centers of the first shield SMT attachments  74  to each other in the first shield SMT center plane, the straight lines combine to define a first shield outer perimeter, wherein each of the first shield SMT attachments  74  defines a node of the first shield outer perimeter. The first nodes can be substantially equidistantly spaced about the first shield outer perimeter. Alternatively, the first nodes can be variably spaced about the first shield outer perimeter as desired. 
     The at least one first electrical signal conductor SMT attachment  35  similarly defines a respective at least one geometric center that lies substantially in a first electrical signal conductor SMT center plane that is oriented perpendicular to the longitudinal direction L. In one example, the first shield SMT center plane is coincident with the first electrical signal conductor SMT center plane so as to define a first common plane with the first electrical signal conductor SMT center plane. The first shield outer perimeter surrounds the at least one geometric center of the at least one first electrical signal conductor SMT attachment  35  in the common plane. It is recognized in other examples that the first shield SMT center plane can be offset from the first electrical signal conductor SMT center plane along the longitudinal direction L. In this example, when the first shield SMT center plane is mapped onto the first electrical signal conductor SMT center plane so as to define a first combined plane with the first shield SMT center plane, the first shield outer perimeter surrounds the at least one geometric center of the at least one first electrical signal conductor SMT attachment  35  in the combined plane. The first electrical shield  44  can carry at least two, at least three, at least four, at least five, at least six, at least seven or at least eight respective first shield SMT attachments  74  as desired that can surround or at least partially surround the at least one, such as at least two, first electrical signal conductor SMT attachments  35 . 
     Similarly, the at least one first conductor mounting portion  34   b  defines a respective at least one geometric center that lies substantially in a first conductor mounting portion plane that is oriented perpendicular to the longitudinal direction L. In one example, the first shield SMT center plane is coincident with the first conductor mounting portion plane so as to define a first common plane with the first conductor mounting portion plane. The first shield outer perimeter surrounds the at least one geometric center of the at least one first conductor mounting portion  34   b  in the common plane. It is recognized in other examples that the first shield SMT center plane can be offset from the first conductor mounting portion plane along the longitudinal direction L. In this example, when the first shield SMT center plane is mapped onto the first conductor mounting portion plane so as to define a first combined plane with the first conductor mounting portion plane, the first shield outer perimeter surrounds the at least one geometric center of the at least one first conductor mounting portion  34   b  in the combined plane. 
     Referring now to  FIG.  1 C  in particular, the second shield SMT attachments  76  that define grounds and can surround either or both of the at least one second electrical signal conductor SMT attachment  37  and the at least one second conductor mounting portion  36   b . In particular, the second shield SMT attachments  76  define respective geometric centers that lie substantially in a second shield SMT center plane that is oriented perpendicular to the longitudinal direction L. When straight lines are drawn that connect adjacent ones of the geometric centers of the second shield SMT attachments  76  to each other in the second shield SMT center plane, the straight lines combine to define a second shield outer perimeter, wherein each of the second shield SMT attachments  76  defines a second node of the second shield outer perimeter. The second nodes can be substantially equidistantly spaced about the second shield outer perimeter. Alternatively, the second nodes can be variably spaced about the second shield outer perimeter as desired. 
     The at least one second electrical signal conductor SMT attachment  37  similarly defines a respective at least one geometric center that lies substantially in a second electrical signal conductor SMT center plane that is oriented perpendicular to the longitudinal direction L. In one example, the second shield SMT center plane is coincident with the second electrical signal conductor SMT center plane so as to define a second common plane with the second electrical signal conductor SMT center plane. The second shield outer perimeter surrounds the at least one geometric center of the at least one second electrical signal conductor SMT attachment  37  in the common plane. It is recognized in other examples that the second shield SMT center plane can be offset from the second electrical signal conductor SMT center plane along the longitudinal direction L. In this example, when the second shield SMT center plane is mapped onto the second electrical signal conductor SMT center plane so as to define a second combined plane with the second shield SMT center plane, the second shield outer perimeter surrounds the at least one geometric center of the at least one second electrical signal conductor SMT attachment  37  in the combined plane. 
     Similarly, the at least one second conductor mounting portion  36   b  defines a respective at least one geometric center that lies substantially in a second conductor mounting portion plane that is oriented perpendicular to the longitudinal direction L. In one example, the second shield SMT center plane is coincident with the second conductor mounting portion plane so as to define a second common plane with the second conductor mounting portion plane. The second shield outer perimeter surrounds the at least one geometric center of the at least one second conductor mounting portion  36   b  in the common plane. It is recognized in other examples that the second shield SMT center plane can be offset from the second conductor mounting portion plane along the longitudinal direction L. In this example, when the second shield SMT center plane is mapped onto the second conductor mounting portion plane so as to define a second combined plane with the second conductor mounting portion plane, the second shield outer perimeter surrounds the at least one geometric center of the at least one second conductor mounting portion  34   b  in the combined plane. The second electrical shield  46  can carry at least two, at least three, at least four, at least five, at least six, at least seven or at least eight respective first shield SMT attachments  76  as desired that can surround or at least partially surround the at least one, such as at least two, first electrical signal conductor SMT attachments  35 . 
     Referring now also to  FIGS.  2 A- 2 G , the SMT attachments  35 ,  37 ,  74 , and  76  can be configured to improve the impedance of the electrical connector system  20 . That is, the electrical connector system  20  can achieve SMT improvements that render measured or simulated impedance closer to a desired impedance. As described above, each of the first and second electrical connectors  22  and  24  can be mounted to respective substrates. In particular, the at least one first electrical signal conductor SMT attachment  35  can be mounted to a respective at least one electrical signal contact pad of a first substrate. Similarly, the first shield SMT attachments  74  can be mounted to respective ones of a plurality of electrical ground contact pads of the first substrate. Similarly, the at least one second electrical signal conductor SMT attachment  37  can be mounted to a respective at least one electrical signal contact pad of a second substrate. Similarly, the second shield SMT attachments  76  can be mounted to respective ones of a plurality of electrical ground contact pads of the second substrate. The first and second substrates can be configured as the substrate  72 . 
     As illustrated in  FIG.  2 A , the substrate  78  includes a dielectric layer  79  such as FR4, at least one electrical signal contact pad  82 , and a plurality of electrical ground contact pads  84 . The ground contact pads  84  can be supported by the dielectric layer  79 . The at least one electrical signal contact pad  82  can be disposed in a respective anti-pad so as to electrically isolate the at least one electrical signal contact pad  82  from the ground layer. 
     Referring now to  FIG.  2 B , the substrate  72  can include at least one electrical signal contact pad  86  and a plurality of electrical ground contact pads  88 . The contact pads  86  and  88  can be referred to as SMT contact pads that are configured to secure to SMT attachments  35  or  37 , and  74  and  76 , respectively. While one single electrical signal contact pad  86  is shown, it should be appreciated that the substrate  72  can include a pair of electrical signal contact pads  86  positioned such that the electrical signal conductor SMT attachments  35  and  37  can be mounted to respective pairs of electrical signal contact pads  86  of first and second ones of the substrate  72  when the first and second electrical connectors  22  and  24  include respective pairs of first and second electrical conductors  28  and  32 . Alternatively, the first and second electrical connectors  22  and  24  can include one single respective signal conductor  28  and  32 , and thus also one signal electrical signal conductor SMT attachments  35  and  37 . Thus, the respective single electrical signal conductor SMT attachments  35  and  37  can be mounted the single electrical signal contact pad  86  of first and second ones of the substrate  72 . The electrical ground contact pads  84  can be positioned such that respective ones of the first and second shield SMT attachments  74  and  76  can be mounted to the ground contact pads  88  of the respective first and second ones of the substrate  72 . 
     The SMT attachments of the first and second electrical connectors  22  and  24 , respectively, can be mounted to respective first sides  72   a  of the substrate  72  to which it is mounted. Thus, the at least one signal contact pad  86  and the electrical ground contact pads  88  can be disposed proximate the first surface  72   a , and accessible from the first side  72   a  by the SMT attachments of the respective one of the first and second electrical connectors  22  and  24 . 
     As illustrated in  FIG.  2 B , the dielectric layer  79  can be flooded with electrically conductive material  90  so as to define a ground plane  92  that encompasses and surrounds the electrical ground contact pads  88  such that external surfaces to which the ground SMT attachments are mounted can be substantially flush with the electrically conductive material. The electrically conductive material  90  can further place the electrical ground contact pads  88  in electrical communication with each other. In one example, the dielectric layer  79  can be flooded with approximate 0.7 mm to 0.8 mm of electrically conductive material  90 . 
     Referring now to  FIGS.  2 C- 2 D , a method can be provided for reducing a pad via stub of a conventional substrate  78  to produce a substrate  72  such as a printed circuit board (PCB) having reduced the pad via stub length SL. In particular, the substrate  72  defines the at least one electrical signal contact pad  86 , and a corresponding at least one electrical signal via  81  that extends from the at least one electrical signal contact pad  86  to a signal trace  83  of the substrate  72 . In some examples, the at least one electrical signal via  81  can extend from the at least one electrical signal contact pad  86  to a second side  72   b  of the substrate  72  that is opposite the first side  72   a . The signal via  81  can be removed, for instance backdrilled, from the second side  72   b  of the substrate  72  toward, but not to, the signal trace  83 . The substrate  72 , and in particular the signal via  81 , can therefore define a pad via stub length  85  that extends along the longitudinal direction L from the signal trace  83  to the second side  72   b  of the substrate  72 . It can be desirable to minimize the stub length  85 , which has been known to have the undesirable effect of acting as an antenna during operation. In one example, the substrate  72  can have a pad via stub length that is half of that of the conventional substrate  78 . In one example, conventional substrates can define pad via stub lengths of approximately 8 mm. The substrate  72  to which a respective one of the first and second electrical connector  22  and  24  is mounted can define pad via stub lengths in a range from approximately 0.5 mm to approximately 4 mm. 
     Referring now to  FIG.  2 E , the solder balls  39  can be more cylindrical than conventional solder balls  94  shown at  FIG.  2 F , which can be configured as solder balls of a NovaRay® electrical connector commercially available from SAMTEC, INC having a principal place of business in New Albany, Ind. The solder balls  39  and  94  are shown in  FIGS.  2 E and  2 F  after a reflow operation that secures the solder balls to a corresponding contact pad of an underlying substrate. 
     The conventional solder ball  94  defines first and second opposed ends  96   a  and  96   b  that are opposite each other along the longitudinal direction L, and a midplane  96   c  that is disposed substantially equidistantly between the opposed ends  96   a  and  96   b  and oriented perpendicular to the longitudinal direction. The conventional solder ball  94  further defines a first intermediate plane  96   d  disposed substantially equidistantly between the first end  96   a  and the midplane  96   c , and a second intermediate plane  96   e  disposed substantially equidistantly between the second end  96   b  and the midplane  96 . The conventional solder ball  94  defines a maximum width at the midplane  96   c , a first width at the first intermediate plane  96   d , and a second width at the second intermediate plane  96   e . The first and second widths can be measured in the same direction as the maximum width. The maximum width is greater than each of the first and second widths. Thus, the reflowed conventional solder balls  94  can be said to have a convex profile. 
     The solder balls  39  of the electrical connector system  20  defines first and second opposed ends  98   a  and  98   b  that are opposite each other along the longitudinal direction L, and a second midplane  98   c  that is disposed substantially equidistantly between the opposed ends  98   a  and  98   b  and oriented perpendicular to the longitudinal direction. Each solder balls  39  further defines a first intermediate plane  98   d  disposed substantially equidistantly between the first end  98   a  and the midplane  98   c , and a second intermediate plane  98   e  disposed substantially equidistantly between the second end  98   b  and the midplane  98   c . Each solder ball  39  defines a maximum width at the midplane  98   c , a first width at the first intermediate plane  98   d , and a second width at the second intermediate plane  98   e . The first and second widths can be measured in the same direction as the maximum width. The maximum width is greater than each of the first and second widths. Thus, the solder balls  39  can be said to have a convex profile. Further, the solder balls  39  can be substantially cylindrical. 
     The convex profile defined by the solder balls  39 , when reflowed onto the substrate, has a more cylindrical shape than the convex profile defined by the reflowed conventional solder balls  96 . In particular, the first and second widths of the solder balls  39  define respective ratios with respect to the maximum width of the solder balls  39  that is greater than respective ratios of the first and second widths of the conventional solder balls  94  with respect to the maximum width of the conventional solder balls. For example, solder ball  39  can have the same height as a conventional solder ball  94  of the NovaRay® vertical board electrical connector commercial available from SAMTEC, INC), but the solder ball  39  can be scaled to have a volume approximately 10-20% less than the conventional solder ball  94  of the NovaRay® vertical board electrical connector commercial available from SAMTEC, INC, such that when the solder ball  39  reflows onto a substrate it forms a barrel in cross-section verses a sphere in cross-section, like the conventional solder ball  94 . The second midplane  98   c  can have a post-board reflow, cross-sectional length of approximately 5-30% less than midplane  96   c . Similarly, the first intermediate plane  98   d  of the respective solder balls  39  can have a post-board reflow, cross-sectional length of approximately 5-30% less than the first intermediate plane  96   d  of the conventional solder ball  94 . Similarly, the second intermediate plane  98   e  of the respective solder balls  39  can have a post-board reflow, cross-sectional length of approximately 5-30% less than the second intermediate plane  96   e  of the conventional solder ball  94 . It has been found that solder balls that reflow to a more cylindrical shape can significantly improve impedance mismatch with respect to the conventional solder ball that reflows to a more circular shape. Thus, the impedance of the electrical connectors  22  and  24  match more closely to the desired impedance. In one example, the first and second widths of the solder balls  39  can be substantially equal to each other. Alternatively, the first and second widths of the solder balls  39  can vary as desired. 
     The shape of solder balls  39  can be intentionally determined by adjusting plating, adjusting connector housing standoff lengths, changing a solder ball size without change a height of the solder ball, changing the contact pad area of the underlying substrate, or widening retention portions of an electrical signal conductor at an intersection of the solder ball and the electrical signal conductor. The step of changing the solder ball size can include reducing a width and/or a depth of the solder ball, without reducing or increasing a height of the solder ball along the transverse direction T. The width can be defined by a first direction that is perpendicular to the transverse direction T, and the depth can be defined by a second direction that is perpendicular to each of the transverse direction T and the first direction. The method of any one of claims  19  to  21  further comprising a step of reducing a width and depth of a solder ball, without reducing or increasing a height of the solder ball. As shown in  FIG.  2 G , the SMT improvements described above, alone or in combination with each other, can improve unwanted impedance mismatch during operation of the electrical connector system  20 , which can be defined as an unwanted variation between a desired impedance and an actual, measured impedance or a simulated impedance. The lighter broken line of  FIG.  2 G  is a simulated single-ended impedance without the SMT improvements described herein, and the solid line of  FIG.  2 G  is a simulated single-ended impedance after the SMT improvements described herein were added to the model. It has been discovered that the electrical connector system  20  can achieve approximately 85 ohms+/5 ohms or approximately 100 ohms+/−5 ohms of differential impedance. 
     Referring now to  FIGS.  1 A- 1 F  and  FIG.  3   , an electrical connector assembly  100  can include an assembly housing  102  and a plurality of electrical connector systems  20  carried or otherwise supported by the assembly housing  102 . In one example, at least respective portions of the electrical connector systems  20  can be disposed in the assembly housing  102 . For instance, the second electrical connector  24 , the second shield  46  and the third shield  54  of each electrical connector system  20  can be carried by the assembly housing  102 . The assembly housing  102  can be configured as a plastic housing, an electrically conductive housing, an electrically conductive magnetic absorbing housing, or an electrically non-conductive magnetic absorbing housing. Thus, the assembly housing  102  can at least partially surround the second shield  46  and the third shield  54 . The first electrical connector  22  and the first shield  44  of each electrical connector system  20  can be carried by the housing  102 , which can be plastic, an electrically conductive and magnetic absorbing, or an electrically non-conductive and magnetic absorbing. Thus, the assembly housing  102  can at least partially surround the first shield  44  and the third shield  54 . As illustrated in  FIG.  3   , four electrical connector systems  20  can be supported by the assembly housing  102 . It should be appreciated, of course, that the electrical connector assembly  100  can include any number of electrical connector systems  20  supported by the assembly housing  102  as desired. 
     It should be appreciated that the electrical connector systems  20  can each be referred to as a respective twinaxial electrical system that includes first twin axial, differential signal electrical connector  22  mated to a second twin axial, differential signal electrical connector  24 . In this regard, the respective pair of first signal conductors  28  of the first electrical connectors  22  can define respective differential signal pairs that are electrically shielded by at least one ground that can be defined by the first and third electrical shields  44  and  54 . Similarly, the respective pair of second signal conductors  32  of the second electrical connectors  24  can define respective second differential signal pairs that are electrically shielded by at least one ground in that can be defined by the second and third electrical shields  46  and  54 . Each electrical connector system  20  can be physically independent of another, and can be physically spaced apart from one another along a plane that is oriented perpendicular to the longitudinal direction L. Each first shield  44  does not share a common wall with another immediately adjacent first shield  44  of an immediately adjacent first electrical connector  22 . Each second shield  46  does not share a common wall with another immediately adjacent second shield  46  of an immediately adjacent second electrical connector  24 . Each third shield  54  does not share a common wall with another immediately adjacent third shield  54  of an immediately adjacent electrical connector system  20 . It should be appreciated that one or more first electrical signal conductor SMT attachments  74  can be eliminated, along with its associated solder pin carried by the first shield mounting portion  44   a , to facilitate substrate routing. Similarly, one or more second electrical signal conductor SMT attachments  76  can be eliminated, along with its associated solder pin carried by the second shield mounting portion  46   a , to facilitate substrate routing. 
     As described above with respect to  FIGS.  1 A- 1 F , the first electrical connector  22  can include at least one first electrical signal conductor  28  that can be configured as a pair of first signal conductors  28 . Further, the second electrical connector  24  can include at least one second electrical signal conductor  32  that can be configured as a pair of second signal conductors  32 . However, referring now to  FIGS.  4 A- 4 B , the first electrical connector  22  can alternatively include a single first electrical signal conductor  28  that can be a first single-ended signal conductor. Similarly, the second connector  24  can alternatively include a single second electrical signal conductor  32  that can be a second single-ended signal conductor. In this regard, the electrical connector systems  10  can be referred to as single-ended connector systems. Further, the electrical connector systems  10  can be referred to as coaxial electrical systems, whereby the respective first and second electrical connectors  22  and  24  define coaxial electrical connectors whose respective single electrical conductors  28  and  32  surrounded by respective shields  44  and  46 . When the first electrical connector  22  is mounted to a respective one of the substrates  72 , the substrate  72  can be configured as a coaxial substrate whose contact pads are SMT contact pads that secure to SMT attachments  35  and  74 . When the second electrical connector  24  is mounted to a respective one of the substrates  72 , the substrate  72  can be configured as a coaxial substrate whose contact pads define SMT contact pads that secures to SMT attachments  37  and  76 . The first and second electrical signal conductors  28  and  32  illustrated in  FIGS.  4 A- 4 B  can be single ended or can define radiofrequency (RF) conductors. The first and second electrical connectors  22  and  24  of  FIG.  4 A  can be carried by our otherwise supported in a respective assembly housing  102  (see  FIG.  3   ) so as to define an electrical connector assembly  100  in the manner described above. 
     As described above, the electrical shields  44  of the first electrical connector can carry a plurality of first shield SMT attachments  74 , such as at least two, at least three, at least four, at least five, or at least six respective first shield SMT attachments  74  that define grounds. The first shield SMT attachments  74  can surround either or both of the electrical signal conductor SMT attachment  35  and the first conductor mounting portion  34   b  of the first electrical signal conductor  28 , in the manner described above. Further, the first shield SMT attachments  74  can define a first shield outer perimeter that surrounds the electrical signal conductor SMT attachment  35  and the first conductor mounting portion  34   b  of the first electrical signal conductor  28 , in the manner described above. The first nodes defined by the first shield SMT attachments  74  can be substantially equidistantly spaced about the first shield outer perimeter. Alternatively, the first nodes can be variably spaced about the first shield outer perimeter as desired. 
     Similarly, as described above, the second electrical shields  46  of the second electrical connector  24  can carry a plurality of second shield SMT attachments  76 , such as at least two, at least three, at least four, at least five, or at least six respective first shield SMT attachments  76  that define grounds. The second shield SMT attachments  76  can surround either or both of the second electrical signal conductor SMT attachment  37  and the second conductor mounting portion  36   b  of the second electrical signal conductor  32 , in the manner described above. Further, the second shield SMT attachments  76  can define a second shield outer perimeter that surrounds the second electrical signal conductor SMT attachment  37  and the second conductor mounting portion  36   b  of the second electrical signal conductor  32 , in the manner described above. The second nodes defined by the second shield SMT attachments  76  can be substantially equidistantly spaced about the second shield outer perimeter. Alternatively, the second nodes can be variably spaced about the second shield outer perimeter as desired. It should be appreciated that one or more first electrical signal conductor SMT attachments  74  can be eliminated, along with its associated solder pin carried by the first shield mounting portion  44   a , to facilitate substrate routing. Similarly, one or more second electrical signal conductor SMT attachments  76  can be eliminated, along with its associated solder pin carried by the second shield mounting portion  46   a , to facilitate substrate routing. 
     Each of the electrical connector systems  20  of  FIG.  4 A  can be independent of another, and are each physically spaced apart from one another. Each first shield  44  does not share a common wall with another immediately adjacent first shield  44  of an immediately adjacent first electrical connector  22 . Each second shield  46  does not share a common wall with another immediately adjacent second shield  46  of an immediately adjacent second electrical connector  24 . Each third shield  54  does not share a common wall with another immediately adjacent third shield  54  of an immediately adjacent electrical connector system  20 . Each first conductor mating portion  34   a  and each second conductor mating portion  36   a  can be solid as described above with respect to  FIGS.  1 A- 1 F  or bifurcated as described above with respect to  FIG.  4 B . 
     It has been found that each of the first and second electrical connectors  22  and  24  having single-ended or differential signal conductors can be cable of transmitting signals at frequencies up to approximately 75 GHz, including up to 67 GHz, with no worse than approximately −60 dB of unwanted cross-talk. Further, each of the first and second electrical connectors  22  and  24  having single-ended or differential signal conductors can be cable of transmitting signals at frequencies up to approximately 75 GHz, including up to 67 GHz, with insertion losses no worse than a range from 0 dB through approximately −3 dB. 
     Although board-to-board connectors are shown, one or both of the first electrical connector  22  and the second electrical connector  24  can be cabled differential signal pair connectors, cabled single-ended connectors, right angled connectors, cabled single-ended connectors, or RF connectors. 
     While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.