Patent Publication Number: US-7722360-B2

Title: Electrical connector with reduced noise

Description:
BACKGROUND OF THE INVENTION 
   The invention relates generally to surface mounted connectors, and more specifically, to a connector that reduces the crosstalk added to signals passing through the connector. 
   The trend toward smaller, lighter, and higher performance electrical components and higher density electrical circuits led to the development of surface mount technology in the design of electrical systems. As is well understood in the art, surface mount packaging allows an electronic package to be attached to pads on the surface of a circuit board, either directly or through a surface mount connector, rather than by means of contacts or pins positioned in plated holes in the circuit board. Surface mount technology allows for an increased component density on a circuit board, thereby saving space on the circuit board. 
   In a connector, with the close proximity of contacts to one another there is a potential for crosstalk and the loss of signal integrity. As signal speeds have increased, crosstalk has become a serious issue. Some circuit boards that carry high speed signals incorporate transmission lines in the board design wherein the width of signal traces and the distance between signal and ground traces are controlled to reduce crosstalk. High speed signals propagate down a transmission line considerably better than down a stand alone trace. However, when the signal encounters a connector, the transmission line is disturbed. Typically, the benefits derived from the transmission line are not maintained as the signal moves through the connector. 
   A need exists for a connector that preserves signal integrity through the connector by reducing crosstalk in the connector. 
   BRIEF DESCRIPTION OF THE INVENTION 
   In one embodiment, an electrical connector is provided. The connector includes a carrier having opposite first and second sides. A plurality of contacts are held in the carrier. Each contact includes a first conductive element and a second conductive element. The first conductive element defines a conductive path configured to electrically connect an electrical component on the first side of the carrier to an electrical component on the second side of the carrier. The second conductive element provides an electrostatic shield for the first conductive element. 
   Optionally, each contact includes an insulative layer having opposite inner and outer sides and wherein one of the conductive elements is formed on the outer side and the other of the conductive elements is formed on the inner side. A plurality of polymer columns are held by the carrier. Each polymer column includes a first end extending from the first side of the carrier and a second end extending from the second side of the carrier. Each contact includes an elongated contact body extending along a longitudinal axis between opposite contact ends. The body includes bends proximate the contact ends that are configured to position the contact ends proximate the first and second ends of one of the polymer columns. The polymer columns are configured to define the mechanical properties of the connector. The carrier includes a plurality of slots and each contact is mounted in one of the slots. A portion of each contact is configured to move within the slot when the contact is compressed. 
   In another embodiment, a contact for an electrical connector is provided that includes a flexible layer of insulative material having opposite inner and outer sides. The flexible layer includes a body that extends along a longitudinal axis between opposite first and second contact ends. A first conductive element is on the outer side of the flexible layer and extends between the first and second contact ends. A second conductive element is on the inner side of the flexible layer and extends along the body. The second conductive element provides an electrostatic shield for the first conductive element. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded view of an electronic assembly including a connector formed in accordance with an exemplary embodiment of the present invention. 
       FIG. 2  is an enlarged view of a portion of an interconnect member formed in accordance with an exemplary embodiment of the present invention. 
       FIG. 3  is a top plan view of the carrier shown in  FIG. 2 . 
       FIG. 4  is a perspective view of a polymer column shown in  FIG. 2 . 
       FIG. 5  is an enlarged top plan view of a contact shown in  FIG. 2  in a flat state. 
       FIG. 6  is a perspective view of the contact shown in  FIG. 5  in a formed condition. 
       FIG. 7  is an enlarged side view of a contact assembly in an uncompressed state. 
       FIG. 8  is an enlarged side view of a contact assembly in a compressed state. 
       FIG. 9  is an enlarged plan view of the front or outer side of an interconnected row of contacts shown in a flat state. 
       FIG. 10  is an enlarged plan view of the back or inner side of the contact row shown in  FIG. 9 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  illustrates an electronic assembly  100  including a connector  110  formed in accordance with an exemplary embodiment of the present invention. The connector  110  is mounted on a circuit board  114  and an electronic package  120  is loaded onto the connector  110 . When loaded onto the connector  110 , the electronic package  120  is electrically connected to the circuit board  114 . In one embodiment, the connector  110  may be a socket connector. The electronic package  120  may be a chip or module such as, but not limited to, a central processing unit (CPU), microprocessor, or an application specific integrated circuit (ASIC), or the like. 
   The connector  110  includes a dielectric housing  116  that is configured to be mounted on the circuit board  114 . The housing  116  holds an interconnect member  124  that includes a plurality of electrical contact assemblies  126 . The electronic package  120  has a mating surface  130  that engages the interconnect member  124 . The interconnect member  124  is interposed between contact pads (not shown) on the mating surface  130  of the electronic package  120  and corresponding contact pads (not shown) on the circuit board  114  to provide electrical paths to electrically connect the electronic package  120  to the circuit board  114  as will be described. It is to be understood, however, that such description is for illustrative purposes only and that no limitation is intended thereby. That is, the interconnect member  124 , in other embodiments, may be used to interconnect two electrical components such as two circuit boards or two electronic packages. Further, although the interconnect member  124  is described with reference to a purely compressive interconnect member, it is to be understood that the interconnect member  124  may also be used in applications where other connection methods, such as solder connections on one or both sides of the interconnect member  124 , are employed. 
     FIG. 2  illustrates an enlarged perspective view of a portion of the interconnect member  124  which is formed in accordance with an exemplary embodiment of the present invention. The interconnect member  124  includes a carrier  134  upon which the contact assemblies  126  are arranged. In one embodiment, the contact assemblies  126  are arranged on opposite sides of a diagonal (not shown) that divides the contact assemblies  126  into two contact groups. The contact assemblies  126  on opposite sides of the diagonal face each other to neutralize frictional forces on the electronic package  120  ( FIG. 1 ) that result from the compression of the contact assemblies  126  that would otherwise tend to push the electronic package  120  toward one corner of the connector  110  ( FIG. 1 ). In some embodiments, the carrier  134  is positioned between compression stops  136 . In such embodiments, the compression stops  136  are provided to limit the compression of the contact assemblies  126  when the electronic package  120  is loaded into the connector  110 . 
   The carrier  134  has a first side  140  and an opposite second side  142 . Each contact assembly  126  includes a polymer column  146  and a contact  150 , both of which are held in the carrier  134 . The polymer columns  146  and contacts  150  are positioned to align with contact pads (not shown) on the electronic package  120  ( FIG. 1 ) and the circuit board  114  ( FIG. 1 ). 
     FIG. 3  illustrates a top plan view of the carrier  134 . The carrier  134  includes a plurality of apertures  160  and slots  162 . The polymer columns  146  ( FIG. 2 ) may be molded onto the carrier  134  at the apertures  160 . In the illustrated embodiment, the apertures  160  are arranged in groups  164  that include three of the apertures  160 , with each group  164  defining a location of one polymer column  146 . It is to be understood however, that other arrangements of apertures  160  are possible including more or fewer apertures  160 . For instance, the apertures  160  in each group  164  may be replaced by a single aperture sized to retain one polymer column  146 . Further, the apertures  160  may take geometric shape other than the circular shapes shown. Each slot  162  has a transverse width  168  that is sized to receive a contact  150  as will be described. In an exemplary embodiment, the carrier  134  may be fabricated from stainless steel. In other embodiments, the carrier  134  may be fabricated from an insulative material such as a polyimide or FR4, which is commonly used for circuit boards. 
     FIG. 4  illustrates a perspective view of the polymer column  146 . Each polymer column  146  includes a first end  170  and an opposite second end  172 . When installed in the carrier  134  ( FIG. 3 ), the first end  170  extends from the first side  140  of the carrier  134  and the second end  172  extends from the second side  142  of the carrier  134 . The polymer column  146  includes a primary column  174  and may also include one or more secondary support columns  176 . The secondary support columns  176 , when present, are provided to stabilize and control the direction of compression of the primary column  174 . The primary column  174  includes a first engagement end  178  that extends from the first side  140  of the carrier  134  and a second engagement end  180  that extends from the second side  142  of the carrier  134 . The polymer columns  146  provide the desired mechanical properties including normal force and working range for the contact assemblies  126 . The polymer columns  146  may be formed from either a pure polymer or a mixed polymer selected to provide desired mechanical properties. In an exemplary embodiment, the polymer columns  146  may be molded directly onto the carrier  134 . 
     FIG. 5  illustrates an enlarged top plan view of a contact  150  in a flat state.  FIG. 6  illustrates a perspective view of the contact  150  in a formed condition as shown in  FIG. 2 . The contact  150  includes a layer of a flexible insulative material  200  such as a polyimide material that includes a front or outer side  202  and an opposite back or inner side  204 . The contact  150  includes a body  210  that extends along a longitudinal axis  212  between opposite contact ends  214  and  216 . The contact body  210  includes a centrally located mounting portion  218  that includes wings  220  with notches  222 . When installed in the carrier  134  ( FIG. 3 ), the wings  220  are configured to frictionally engage the carrier  134  while allowing some degree of movement between the contact body  210  and the carrier  134 . A first conductive element  230  is formed on the outer side  202  of the flexible layer  200  and includes contact tips  232  and  234 . A second conductive element  240  is formed on the inner side  204  of the flexible layer  200 . In an exemplary embodiment, the flexible layer  200  is fabricated from a flexible polyimide material. One such polyimide material is commonly known as Kapton® which is available from E. I. du Pont de Nemours and Company. The conductive elements  230  and  240  may be formed from copper that may be etched or otherwise adhered to the flexible layer  200 . After application of the conductive elements  230  and  240  to the flexible layer  200 , the contacts  150  are formed to their final shape as shown in  FIG. 6 . 
   With renewed reference to  FIG. 3 , each slot  162  in the carrier  134  is configured to hold a contact  150 . Each slot  162  has a transverse width  250  that is sized to receive a transverse width  252  of the contact body  210  at the notches  222  while the wings  220  have a transverse width  254  that is greater than the width  250  of the slot  162 . When installed in the carrier  134 , the notches  222  of the contact body  210  fit within the slot  162  while the wings  220  engage the first and second sides  140  and  142 , respectively, of the carrier  134  so that the conductive elements  230  and  240  are isolated from the carrier  134 . 
   The contact  150  is formed such that the contact body  210  includes a centrally located bend  260  that facilitates flexing of the contact body  210  when interposed and compressed between two electrical components such as the electronic package  120  ( FIG. 1 ) and the circuit board  114  ( FIG. 1 ). The contact body  210  includes bends  262  at each contact end  214  and  216 . When the contact  150  is installed in the carrier  134 , the contact body  210  extends through the carrier  134 . The contact  150  is positioned and dimensioned such that the contact tips  232  and  234  are proximate the engagement ends  178  and  180  of one of the polymer columns  146  and oriented for accurate registration with the contact pads (not shown in  FIG. 4 ) on the circuit board  114  and the electronic package  120 . 
   The first conductive element  230  defines a conductive path that electrically connects a first electrical component such as the electronic package  120  on the first side  140  of the carrier  134  to a second electrical component such as the circuit board  114  on the second side  142  of the carrier  134 . In an exemplary embodiment, the second conductive element  240  does not establish a conductive path between electrical components. More specifically, the second conductive element  240  is generally not current carrying. Rather, the second conductive element  240  is held at ground potential and acts as a ground. On each contact  150 , the second conductive element  240  is much closer to the first conductive element  230  than any adjacent contact  150 , such that when the first conductive element  230  is signal carrying, the second conductive element  240  electromagnetically couples with the first conductive element  230  and acts as an electrostatic shield. The electrostatic shielding provided by the second conductive element  240  reduces electromagnetic coupling between neighboring contacts  150  to thereby reduce the crosstalk that occurs between neighboring contacts  150  in the connector  110 . 
     FIG. 7  illustrates an enlarged side view of the contact assembly  126  in an uncompressed state.  FIG. 8  illustrates an enlarged side view of the contact assembly  126  in a compressed state. When the contacts  150  are loaded into the carrier  134 , the slots  162  in the carrier  134  provide clearance space for flexing of the contacts  150 . The wings  220  frictionally engage the first and second sides  140  and  142  respectively of the carrier  134  sufficiently to prevent the contact ends  214  and  216  from becoming disengaged from the polymer columns  146  while permitting the contact body  210  to move in the direction of the arrow A within the slot  162  to flex in response to a compressive load on the contact assembly  126 . Coincident with the flexing of the contact  150 , the polymer column  146 , and particularly the primary column  174 , is compressed in response to the compressive load on the contact assembly  126 . 
   The flexible layer  200  of the contact  150  has a thickness  270  which represents a distance between the first conductive element  230  and the second conductive element  240 . At such distances, when the first conductive elements  230  are signal carrying and the second conductive element  240  is at ground, and more particularly, a non-current carrying ground, the signal and ground are tightly electromagnetically coupled to one another rather than the signal being coupled to a signal carried in an adjacent contact  150 . That is, the second conductive element  240  electrostatically shields the signal carried in the first conductive element  230  such that crosstalk introduced in the connector  110  is reduced even at high contact densities. In this manner, degradation of signal integrity through the connector  110  is minimized. In  FIGS. 7 and 8 , the second conductive element  240  is shown as extending to the engagement ends  178 ,  180  of the primary polymer column  174 . However, in other embodiments, the second conductive element  240  need not extend to the engagement ends  178 ,  180  of the primary polymer column  174 . 
     FIG. 9  illustrates an enlarged plan view of a contact row  300  shown in a flat state and taken from a front or outer side  302 .  FIG. 10  illustrates an enlarged plan view of a back or inner side  304  of the contact row  300 . The contact row comprises a number of interconnected contacts  310  and  312 . Each contact  310 ,  312  includes a flexible layer  320  that has wings  322  with notches  324  as previously described with respect to the contact  150  ( FIG. 5 ). The wings  322  of each contact  310 ,  312  are joined to the wings  322  of adjacent contacts  310 ,  312  by an interconnecting portion  326  to interconnect the contacts  310 ,  312  and form the contact row  300 . The interconnections between the contacts  310 ,  312  are all on the same side of the notches  324  which facilitates loading of the contact row  300  onto the carrier  134  ( FIG. 3 ) as a unit. 
   Each contact  310  includes a first conductive element  330  formed on the outer side  302  of the contact row  300  that extends between opposite contact ends  332  and  334  of the contact  310 . The first conductive element  330  is identical to the first conductive element  230  ( FIG. 5 ) previously described. Each contact  310  also includes a second conductive element  340  on the inner side  304  of the contact row  300 . The second conductive element  340  includes lateral extensions  342  that extend along the inner side of the interconnecting portions  326  of the flexible layer  320  to electrically connect the second conductive element  340  of each contact  310  to the second conductive element  340  of an adjacent contact  310  or  312  in the contact row  300 . As previously described, on each contact  310 , the second conductive element  340  is at ground potential and electromagnetically couples with the first conductive element  330  to provide an electrostatic shield for the first conductive element  330 , thereby reducing crosstalk between neighboring contacts  310 . 
   Each contact  312  includes a first conductive element  350  formed on the outer side of the contact row  300  and a second conductive element  352  formed on the inner side of the contact row  300 . The first conductive element  350  extends between contact ends  354  and  356  and is identical to the first conductive element  330  on the contact  310  with the exception that the first conductive element  350  may include one or more vias  358  that also extend at least through the flexible layer  320  to enable the establishment of electrical connectivity with the second conductive element  352 . Although the via  358  is shown as extending through the first and second conductive elements  350  and  352 , it is to be understood that the via  358  may be formed only in the flexible layer  320  and connectivity between the first and second conductive elements  350  and  352  may be established by such means as plating the via or filling the via with a conductive material. 
   The second conductive element  352  includes lateral extensions  360  that extend along the inner side of the interconnecting portions  326  of the flexible layer  320  to interconnect the second conductive element  352  with the second conductive elements of the contacts  310  or additional contacts  312 , as described above with respect to the lateral extension  342  of the contact  310 . After the conductive elements  350  and  352  are applied to the flexible layer  320 , the contacts  310  and  312  are formed to their final shape which is similar to that of the contact  150  as shown in  FIG. 6 . 
   As illustrated in  FIGS. 9 and 10 , the contact row  300  includes one of the contacts  312 , however, in other embodiments, more or no contacts  312  may be present. With regard to the contact  312 , the second conductive element  352  is shown as extending between the contact ends  354  and  356 , and is configured to rest upon the engagement ends  178  and  180  of one of the primary polymer columns  174  when loaded into the carrier  134 . However, in other embodiments, the second conductive element  352  need not extend to the engagement ends  178 ,  180  of the primary polymer column  174 . 
   When the second conductive element  352  does not extend to the engagement ends  178  and  180 , a via may be placed elsewhere along the first and second conductive elements  350  and  352  respectively, or at least in the flexible layer  320  between the first and second conductive elements  350  and  352  to provide for the establishment of an electrical connection between the first and second conductive elements  350  and  352 . In some embodiments, the second conductive element  352  may be configured to engage the carrier  134  when the carrier  134  is fabricated from a conductive material such as stainless steel. To reiterate, this is done only for the contacts  312 . Further, it is to be understood, that by electrically interconnecting the first and second conductive elements  350  and  352  to one another, the contact  312  is a dedicated ground contact that is configured to interconnect dedicated ground circuits (not shown) on the electronic package  120  ( FIG. 1 ) and the circuit board  114  ( FIG. 1 ), or more generally on each of two electronic components (not shown). 
   The embodiments thus described provide a connector  110  that preserves signal integrity through the connector  110  by reducing crosstalk introduced in the connector  110 . The connector  110  includes a contact  150  having at least two separate conductive elements  230 ,  240  formed on opposite sides of a flexible layer  200 . The conductive element  240  on the inner side  204  of the flexible layer  200  provides electrostatic shielding for the conductive element  230  on the outer side  202  of the flexible layer  200  to thereby reduce crosstalk in the connector  110 . Alternatively, the contacts are formed in a contact row  300  including contacts  310  formed on interconnected flexible layers  320 . The conductive elements  340  on the inner side  304  of the flexible layers  320  are interconnected and provide shielding. The contact row  300  may also include a dedicated ground contact  312  having first and second conductive elements  350  and  352  that are electrically connected through a via  358 . 
   While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.