Abstract:
The present invention is directed to a high density electrical connector which can provide 80 or more twinax connections per linear inch in a 20 millimeter card slot. In a typical electronic system package, 20 millimeters is the spacing from center line to center line of the adjacent parallel daughtercards. Twinax cable is coaxial cable that contains two inner conducting wires rather than one. The two inner conducting wires provide two physical channels. Coaxial cable is called “coaxial” because it includes one physical channel that carries the signal surrounded (after a layer of insulation) by another concentric physical channel, both running along the same axis. The outer channel serves as ground.

Description:
RELATED APPLICATION  
       [0001]    The present application claims priority of provisional patent application Serial No. 60/260,893 filed Jan. 12, 2001, entitled “HIGH SPEED, HIGH DENSITY INTERCONNECT SYSTEM FOR DIFFERENTIAL AND SINGLE-ENDED TRANSMISSION APPLICATIONS” and provisional patent application Serial No. 60/328,396 filed Oct. 12, 2001, entitled “HIGH SPEED, HIGH DENSITY INTERCONNECT SYSTEM FOR DIFFERENTIAL AND SINGLE-ENDED TRANSMISSION APPLICATIONS”, the disclosures of which are hereby incorporated by reference in their entirety into the present specification. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates generally to electrical connectors, and more particularly, to a high speed, high density interconnect system for differential and single-ended transmission applications. The present invention relates to a latching mechanism for compression mount type electrical connectors. The present invention also relates to a high speed, high density electrical connector having a central twinax or coax portion and fuzz button contacts on opposite ends of the central twinax or coax portion. The present invention also relates to an apparatus for installing fuzz buttons without the need for sockets at opposite ends of the fuzz button.  
         BACKGROUND OF THE INVENTION  
         [0003]    Backplane systems are comprised of a complex printed circuit board which is referred to as the backplane or motherboard, and several smaller printed circuit boards which are referred to as daughtercards which plug into the backplane. Each of the daughtercards include a chip which is referred to as a driver/receiver. The driver/receiver sends and receives signals from driver/receivers on other daughtercards. A signal path is formed between the driver/receiver on a first daughtercard and a driver/receiver on a second daughtercard. The signal path includes an electrical connector that connects the first daughtercard to the backplane, the backplane, a second electrical connector that connects the second daughtercard to the backplane, and the second daughtercard having the driver/receiver that receives the carried signal. Various driver/receivers being used today can transmit signals at data rates between 5-10 Gb/sec and greater. The limiting factor (data transfer rate) in the signal path are the electrical connectors which connect each daughtercard to the backplane. A need thus exists in the art for a high speed electrical connector capable of handling the required high speed transfer of data.  
           [0004]    Further, the receivers are capable of receiving signals having only 5% of the original signal strength sent by the driver. This reduction in signal strength increases the importance of minimizing cross-talk between signal paths to avoid signal degradation or errors being introduced into digital data streams. With high speed, high density electrical connectors, it is even more important to eliminate or reduce cross-talk. Thus, a need exists in the art for a high speed electrical connector capable of handling high speed signals that reduces cross-talk between signal paths.  
           [0005]    There are various types of electrical connectors. One type is a through hole connector which could either be a compliant pin or through hole solder. Backplane systems have typically used connectors which consist of multiple contacts having pins which are inserted into the through hole contained in the printed circuit boards to be connected. The pins can be compliant fit or can be soldered in place. These require a relatively large diameter hole in the printed circuit board for receiving the pins of the connector. The larger the hole the greater the probability of defects from plating and the greater the capacitance which reduces the signal speed which can be accommodated by these connectors. For example, plated through holes may not be properly plated and thus pins being inserted from the electrical connector can cause open shorts, etc. The plated through hole causes a capacitive effect which reduces the data rate which can be transferred through the pin and hole. Further, many contact type connectors are made from stamped parts which have varying geometries which increase signal reflection and reduce signal speed. Thus, it is advantageous to reduce the diameter of plated through hole sizes using a compression mount-type connectors which rely on a spring making contact with a pad on a board.  
           [0006]    Many of these problems can be solved using a compression mount type electrical connector. This type of connector overcomes many of the deficiencies of the through hole contact type but compression mount connectors need bulky and expensive hardware to fasten the compression mount connector to the printed circuit board. Intimate contact needs to be maintained between compression mount contacts and the PC board surface without using additional fasteners such as jack screws.  
           [0007]    Additionally, regardless of the type of electrical connector, the electrical connector has to be capable of being mated/unmated at least 250 and perhaps in excess of 1000 times. If the contacts wear, then contact resistance will increase. Contact wear can occur through metal to metal contact either through a point or line. For example, a certain area may continually get wiped as the connector is mated/unmated and the contact tends to wear through the metal sliding action can also cause wear. Also, some compression mount type connectors use dendrite contacts on flexible circuits. One difficulty with dendrite contacts is that these contacts tend to wear and are only good for a half a dozen mating cycles and the dendrites start to flatten out and the multiple points of contacts are lost thereby reducing reliability. Thus, a need exists for a compression mount-type connector that eliminates or reduces contact wear.  
           [0008]    Another problem with prior art electrical connectors is that impedance changes over the length of the signal path reduce the potential signal speed. A need exists for an electrical connector in which impedance can be controlled at a specific value and where the specific value remains relatively constant over the length of the signal path.  
           [0009]    In summary, electrical connectors used to electrically connect circuit boards such as backpanels to daughtercards suffer from several deficiencies including poor shielding resulting in electrical noise, changes in impedance and the inability to connect and disconnect many times without damage to the electrical connector. These deficiencies limit the data rate that can be transferred through the connector. Thus, a need exists in the art for a high density electrical connector which overcomes the aforementioned problems to a large extent.  
         SUMMARY OF THE INVENTION  
         [0010]    It is an object of the present invention to provide an electrical interconnect system capable of carrying signals at data rates between 5-10 Gb/sec or more.  
           [0011]    It is another object of the present invention to provide a compression mount type connector having a simple and elegant latching mechanism for keeping the electrical connector in contact with each PC board.  
           [0012]    Still another object of the present invention is to provide an electrical connector having a differential pair having constant impedance over the signal path and capable of carrying signals at between 5-10 Gb/sec or more.  
           [0013]    Yet another of the present invention is to provide a coaxial cable connector having constant impedance over the signal path and capable of carrying signals at data rates between 5-10 Gb/sec or more.  
           [0014]    Another object of the present invention is to provide an electrical connector in which cross-talk between signal paths of adjacent twinax cables or adjacent coaxial cables within the electrical connector is reduced and/or eliminated.  
           [0015]    Yet another object of the present invention is to provide a compression type electrical connector using fuzz buttons or some other conductive spring configuration.  
           [0016]    Still another object of the present invention is to provide a means of protecting fuzz buttons when the electrical connector is not connected.  
           [0017]    The present invention is directed to a high density electrical connector which can provide 80 or more twinax connections per linear inch in a 20 millimeter card slot. In a typical electronic system package, 20 millimeters is the spacing from center line to center line of the adjacent parallel daughtercards. Twinax cable is coaxial cable that contains two inner conducting wires rather than one. The two inner conducting wires provide two physical channels. Coaxial cable is called “coaxial” because it includes one physical channel that carries the signal surrounded (after a layer of insulation) by another concentric physical channel, both running along the same axis. The outer channel serves as ground.  
           [0018]    In a first embodiment, the electrical connector according to the present invention utilizes fuzz buttons positioned in a daughtercard interposer and a backpanel interposer electrically to connect the two inner signal carrying conductor wires to conductive pads on a printed circuit board. Shielding members of the fuzz buttons are used to surround stripped (unshielded) sections of twinax cable and to electrically connect the outer jacket to ground planes in the daughtercard and the backpanel and to provide shielding between the closely spaced conductors. Advantageously, the present invention permits the impedance of the connector to be controlled by changing the dielectric thickness and constants.  
           [0019]    These and other objects of the present invention are achieved by an interconnect system, including a first interposer housing including a first plurality of shielding members providing shielding for the thickness of the first interposer. A second interposer housing includes a second plurality of shielding members providing shielding for the thickness of the second interposer. At least one cable has a central conductor, a conductive outer jacket, and a dielectric separating the central conductor and the conductive outer jacket. The outer jacket is in electrical contact with at least some of the plurality of shielding members in the first interposer housing and the second interposer housing. A cable housing is connected to the first interposer and to the interposer for retaining the at least one cable. The at least one cable has exposed portions extending beyond the cable housing into the first interposer and the second interposer, respectively. At least one conductive element is in contact with a central conductor of the at least one cable.  
           [0020]    The foregoing and other objects of the present invention are achieved by an electrical connector, including a central cable surrounded by a dielectric layer and an electrically conductive jacket. The central cable has exposed opposite ends. A first plurality of shielding members are in electrical contact with one end of the electrically conductive jacket. A second plurality of shielding members are in electrical contact with an opposite end of the electrically conductive jacket. A first conductive element is in contact with one of the exposed opposite ends of the central cable. A second conductive element is in contact with an opposite exposed end of central cable.  
           [0021]    The foregoing and other objects of the present invention are achieved by a twinax electrical connector, including a twinax cable having two electrical conductors spaced from each other and having a dielectric surrounding the two electrical conductors and an electrically conductive layer surrounding the dielectric. The two electrical conductors each have exposed opposite ends. A first plurality of shielding members are in electrical contact with one end of the electrically conductive jacket. A second plurality of shielding members are in electrical contact with an opposite end of the electrically conductive jacket. A first set of conductive elements are each in contact with a corresponding one exposed end of the two electrical conductors. A second set of conductive elements are each in contact with a corresponding second exposed end of the two electrical conductors.  
           [0022]    The foregoing and other objects of the present invention are achieved by a method of transmitting a differential signal using an electrically shielded twinax cable includes carrying a first signal and a second signal each on a separate conductor of the twinax cable and shielding the separate conductors from adjacent conductors without shielding the separate conductors from each other and measuring the difference at a receiver between the first and second signal to arrive at an actual signal pulse.  
           [0023]    The foregoing and other objects of the present invention are achieved by a matching mechanism for a compression mount connector. The compression mount connected is mountable to a printed circuit board. A guide pin is mounted to the printed circuit board. The guide pin has a groove thereabout. A guide block has a biased latching device for engaging the groove when the guide pin groove is brought into engagement therewith. The electrical connector has contacts which exert a force in a direction away from the electrical connector being in a mated condition with contacts on the circuit board and the latching mechanism is capable of resisting the force such that the contacts in the electrical connector remain in contact with the contacts on the circuit board.  
           [0024]    The foregoing and other objects of the present invention are achieved by an electrical connector having a plurality of twinax cables arranged in a vertical and horizontal array. A first set of twinax cables are arranged in a vertical array and spaced from each other. Each twinax cable has a pair of conductors, a dielectric layer and an electrically conductive jacket. A second set of twinax cables are arranged in a vertical array and spaced from each other and horizontally spaced from the first set of twinax cables. A first plurality of conductive elements are each positioned against a corresponding conductor. A second plurality of conductive elements are each positioned against a corresponding conductor. A cable housing retains the first set and the second set of twinax cables. A first interposer is on one side of the cable housing for receiving one end of the first set and the second set of twinax cables. A second interposer is on another side of the cable housing for receiving an opposite end of the first set and the second set of twinax cables. A first retaining sheet retains signal spring contacts in contact with each pair of conductors on the one end of the first and second set of twinax cables. A second retaining sheet retains signal spring contacts in contact with each pair of conductors on the opposite end of the first and second set of twinax cables. A first interposer slide is biased in a direction away from the first interposer and receives an opposite end of the signal conductors and has a retracted position and a normal extended position. A second interposer slide is biased in a direction away from the second interposer and receives an opposite end of the signal conductors and has a retracted position and an extended position. The conductive elements are retained by the first retaining sheet and the second retaining sheet and are protected by the first interposer slide and the second interposer slide, respectively, when each is in the retracted position. The first plurality and the second plurality of conductive elements extend beyond the first interposer slide and the second interposer slide, respectively, when each is in the normal extended position.  
           [0025]    The foregoing and other objects of the present invention are achieved by an electrical interconnect system, including at least one cable having at least one central conductor and a conductive outer jacket with an insulator therebetween. A set of cable housings retains at least one cable. A first interposer cable housing has a first plurality of through holes corresponding to the at least one central conductor and a second plurality of holes partially overlapped in a radial direction with a respective one of the conductive outer jackets. A second interposer cable housing has a third plurality of through holes corresponding to the at least one central conductor and a fourth plurality of holes partially overlapped in a radial direction with a respective one of the conducive outer jackets. A first plurality of electrically conductive elements is inserted into the first plurality of through holes in the first interposer. A second plurality of electrically conductive elements is inserted into the second plurality of holes in the first interposer. A first interposer slide includes a first interposer cable housing having a first plurality of through holes corresponding to the at least one central conductor. A second plurality of holes is partially overlapped in a radial direction with a respective one of the conductive outer jackets. A first retainer positioned between the first interposer cable housing and the first interposer slide retains the first plurality of electrically conductive elements and the second plurality of electrical conductive elements. A second interposer cable housing has a third plurality of through holes corresponding to the at least one central conductor. A fourth plurality of holes is partially overlapped in a radial direction with a respective one of the conductive outer jackets. A third plurality of electrically conductive elements is inserted into the third plurality of through holes in the second interposer. A fourth plurality of electrically conductive elements is inserted into the fourth plurality of holes in the second interposer. A second interposer slide includes a third interposer cable housing having a third plurality of through holes corresponding to the at least one central conductor. A fourth plurality of holes is partially overlapped in a radial direction with a respective one of the conductive outer jackets.  
           [0026]    The foregoing and other objects of the present invention are achieved by a latching mechanism for a compression mount type connector, including a garter spring retained in the compression mount type connector. A guide pin extends from a circuit board and has an annular inwardly extending groove for receiving an inner diameter of the garter spring.  
           [0027]    The foregoing and other objects of the present invention are achieved by a compression mount electrical connector for mounting to a printed circuit board having a guide pin and including a housing with a plurality of signal paths. A latching mechanism includes a latching device in the housing for latching onto the guide pin.  
           [0028]    The foregoing and other objects of the present invention are achieved by a twinax electrical connector including a latching device. A twinax cable has two electrical conductors spaced from each other and has a dielectric surrounding the two electrical conductors and an electrically conductive layer surrounding the dielectric. The two electrical conductors has exposed opposite ends. A first plurality of shielding members is in electrical contact with one end of the electrically conductive jacket. A second plurality of shielding members is in electrical contact with an opposite end of the electrically conductive jacket. A first set of conductive elements is in contact with a corresponding one exposed end of the two electrical conductors. A second set of conductive elements is in contact with a corresponding one exposed end of the two electrical conductors. A second set of conductive elements is in contact with a corresponding second exposed end of the two electrical conductors. A latching mechanism includes a latching device in the housing for latching onto the guide pin.  
           [0029]    The foregoing and other objects of the present invention are achieved by an electrical connector having a plurality of twinax cables arranged in a vertical and horizontal array and having a latching mechanism. A first set of twinax cables is arranged in a vertical array and spaced from each other. Each twinax cable has a pair of conductors, a dielectric layer and an electrically conductive jacket. A second set of twinax cables is arranged in a vertical array and spaced from each other and horizontally spaced from the first set of twinax cables. A first plurality of conductive elements is each positioned against a corresponding conductor. A second plurality of conductive elements is each positioned against a corresponding conductor. A cable housing is retained in the first set and the second set of twinax cables. A first interposer on one side of the cable housing is for receiving one end of the first set and the second set of twinax cables. A second interposer on another side of the cable housing is for receiving an opposite end of the first set and the second set of twinax cables. A first retaining sheet is for retaining signal spring contacts in contact with each pair of conductors on the one end of the first and second set of twinax cables. A second retaining sheet is for retaining signal spring contacts in contact with each pair of conductors on the opposite end of the first and second set of twinax cables. A first interposer slide is biased in a direction away from the first interposer and receives an opposite end of the signal conductors and has a retracted position and a normal extended position. A second interposer slide is biased in a direction away from the second interposer and receives an opposite end of the signal conductors and has a retracted position and an extended position. The conductive elements are retained by the first retaining sheet and the second retaining sheet and are protected by the first interposer slide and the second interposer slide, respectively, when each is in the retracted position. The first plurality and the second plurality of conductive elements extend beyond the first interposer slide and the second interposer slide, respectively, when each is in the normal extended position. A latching mechanism includes a latching device in the housing for latching onto the guide pin.  
           [0030]    Advantageously, the present invention utilizes printed circuit board space more efficiently than traditional press fit connectors and provides improved shielding for the signal carrying central conductors.  
           [0031]    The present invention is also directed to a packaging system for retaining fuzz buttons which are used as either ground contacts or signal contacts in the high density electrical connector.  
           [0032]    The present invention also is directed to a means of protecting fuzz buttons when not in contact with a conductive trace on a printed circuit board and/or when the electrical connector is not connected to a printed circuit board.  
           [0033]    The present invention can also be used to protect fuzz buttons. As can be appreciated, the fuzz buttons or the wadded wire cylinders are easily damaged if exposed. To protect the fuzz buttons, sockets have been used at opposite ends of the fuzz buttons and/or precise drilled holes to retain the fuzz buttons.  
           [0034]    The sockets protect opposite ends of the fuzz buttons which are installed in through bores. The fuzz button is placed in the throughbore and the movable sockets or top hats are positioned at opposite ends of the throughbore and are spring loaded by the fuzz buttons to extend beyond the throughbore. Thus, the fuzz buttons are completely surrounded and are protected.  
           [0035]    For example, cylindrical button contacts of wadded fine conductor wires have been inserted axially into generally uniform cylindrical holes which were formed in the substrate such as by acid etching of ceramicized glass substrates or drilling a laminated or sheet plastic insulator sheet. The button wads fill the respective holes and are held in place in their corresponding holes by compressive radial frictional engagement with the side walls of each of the holes. Because of this relationship, insertion of the button wads into their respective holes has been a difficult process.  
           [0036]    Still other advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein the preferred embodiments of the invention are shown and described, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description thereof are to be regarded as illustrative in nature, and not as restrictive.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0037]    The present invention is illustrated by way of example, and not by limitation, in the figures of the accompanying drawings, wherein elements having the same reference numeral designations represent like elements throughout and wherein:  
         [0038]    [0038]FIG. 1A is a perspective view of an electrical connector according to the present invention mounted to a daughtercard and a backplane with an over-mold omitted for clarity;  
         [0039]    [0039]FIG. 1B is the same view as FIG. 1A with the over-mold depicted;  
         [0040]    [0040]FIG. 2 is a perspective view of the electrical connector according to the present invention with the semi-rigid twinax connected to the back panel interposer only and with the backpanel and over-mold omitted for clarity;  
         [0041]    [0041]FIG. 3 is a bottom perspective view of FIG. 2;  
         [0042]    [0042]FIG. 4 is the same view as FIG. 2 with the back panel interposer omitted for clarity;  
         [0043]    [0043]FIG. 5 is the same view as FIG. 4 with some of the fuzz buttons omitted for clarity;  
         [0044]    [0044]FIG. 6 is the same view as FIG. 5 with additional fuzz buttons omitted for clarity;  
         [0045]    [0045]FIG. 7 is a bottom perspective view with the fuzz buttons omitted for clarity;  
         [0046]    [0046]FIG. 8 is a perspective view of the daughtercard and backpanel including PC board patterns;  
         [0047]    [0047]FIG. 9 illustrates a backpanel, mid-panel and daughtercard in an actual application;  
         [0048]    [0048]FIG. 10 is an exploded view of a second embodiment of an electrical connector according to the principles of the present invention;  
         [0049]    [0049]FIG. 11 is an enlarged exploded view of the cable housing interposers according to the present invention;  
         [0050]    [0050]FIG. 12 is an enlarged view of a front side of the interposer cable housing shown in FIG. 10 according to the present invention;  
         [0051]    [0051]FIG. 13A is a perspective view of the electrical connector of the present invention mounted to a daughtercard with the daughtercard interposer slide being in a retracted position and the backpanel interposer slide being in an extended position;  
         [0052]    [0052]FIG. 13B is a cross-sectional view of fuzz buttons being retained by the mylar sheet illustrating one end of the fuzz buttons within the interposer slide when the interposer slide is in an extended position;  
         [0053]    [0053]FIG. 13C is a cross-sectional view similar to FIG. 13B illustrating the one end of the fuzz buttons extending beyond the interposer slide when the interposer slide is in a retracted position;  
         [0054]    [0054]FIG. 14 is a view of the interposer slide mating face;  
         [0055]    [0055]FIG. 15 is an exploded view of a latching guide module according to the present invention;  
         [0056]    [0056]FIG. 16 depicts the electrical connector mounted to a daughtercard with the daughtercard interposer slide in a retracted engaged position and a backpanel interposer slide in an extended unengaged position;  
         [0057]    [0057]FIG. 17 depicts the electrical connector mounted to a daughtercard and mated to a backpanel;  
         [0058]    [0058]FIG. 18 depicts the guide module, in a fully mated state, with one half of the housing omitted to expose the operating components of the assembly;  
         [0059]    [0059]FIG. 19 depicts the guide module, in an unmated state, with one half of the housing removed and the guide socket omitted to expose the operating components of the assembly;  
         [0060]    [0060]FIG. 20 depicts the guide module, in a partially mated state, with one half of the housing removed and the guide socket omitted to expose the operating components of the assembly. This illustrates the movement of the springs and latching devices during the mating process;  
         [0061]    [0061]FIG. 21 depicts the guide module, from the back side, with the guide pin in the full installed position;  
         [0062]    [0062]FIG. 22 shows the guide module, from the back side, without the guide pin installed and the guide socket removed with the latching devices in the “closed” position;  
         [0063]    [0063]FIG. 23 is the same as FIG. 22 with the guide socket in place with the latching devices in the “closed” position;  
         [0064]    [0064]FIG. 24 is a view from the same direction as in FIGS.  21 - 23 . It illustrates the latching devices in the full “open” position during the mating cycle;  
         [0065]    [0065]FIG. 25 is a perspective view with the guide pin engaged with a latching device and the cable housing and some latching devices and springs omitted for clarity; and  
         [0066]    [0066]FIG. 26 depicts a second embodiment of a latching mechanism according to the principles of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0067]    The interconnect arrangement according to the present invention provides a unique twin axial shielded coax structure that has constant impedance from daughtercard interface to the backplane interface. The coaxial structure provides for constant impedance of 65 ohms single ended impedance, 50 ohms odd mode impedance and 100 ohms differential impedance. Advantageously, the present invention provides a controlled impedance connector through the ability to change the characteristic impedance of the electrical connector by changing the dielectric thickness and constant. This allows custom connectors to be made at different impedance values ranging from 35 ohms to 150 ohms or higher.  
         [0068]    A single ended interconnect path utilizes one conductor to transfer data. A differential interconnect path utilizes two conductors to transmit the same data. The benefit of a differential interconnect path relative to a single ended interconnect path is that transmission speed increases and noise immunity and electromagnetic interference (EMI) concerns are reduced.  
         [0069]    Utilizing the twinax design according to the present invention, the connector design described herein will provide the best known practice for transmitting differential data utilizing copper conductors. The same is true for the single ended version. The single ended design utilizes a coaxial conductor to transmit data. This makes it possible to transmit analog (RF) or digital data with signal degradation comparable to that of a coaxial cable.  
         [0070]    Refer first to FIGS. 1A and 1B where an interconnect system for a high speed, high density interconnect path is illustrated. FIG. 1A shows the electrical connector with the over-mold omitted for simplicity of explanation. The connector  18  is used to electrically connect daughtercard  20  to a backpanel  22 . The connector  18  includes, as depicted in FIG. 1B, a daughtercard interposer  30 , a backpanel interposer  32 , an over-mold  34  which over-molds semi-rigid twinax or coax cables. The over-mold  34  is preferably injection molded, for example, from PBT (polybutylene terephthalate). As depicted in FIGS. 1A and 1B, only two twinax cables  40 ,  42  are shown for ease of illustration, although it is anticipated that 80 pairs or more of twinax would be used in the electrical connector according to the present invention. The presently preferred embodiment uses twinax cable which is bent into a desired shape. The present invention also contemplates the use of a more rigid construction which is molded in a single piece. For the cables  40 ,  42  the center conductor is copper, the dielectric material is preferably Teflon™ and the outside jacket is a braid. Preferably, the differential impedance between center conductors is approximately 100 ohms. Using standard formulas, the impedance can easily be adjusted by varying the distance between center conductors and the dielectric constant for example. In FIG. 1A, the over-mold  34  is omitted for clarity. As depicted in FIGS. 1A and 1B, fuzz button arrangements  50 ,  52 ,  60 ,  62  are positioned within the interposers  30 ,  32 , respectively, and surround ends of the twinax cables  40 ,  42  in order to shield the twinax cables and control the impedance of the connector.  
         [0071]    Fuzz buttons and the uses thereof are explained in U.S. Pat. No. 4,998,306, issued Jan. 29, 1991, entitled “LOW-LOSS ELECTRICAL INTERCONNECTS”, U.S. Pat. No. 5,886,590, issued Mar. 23, 1999, entitled “MICROSTRIP TO COAX VERTICAL LAUNCHER USING FUZZ BUTTON AND SOLDERLESS INTERCONNECTS”, U.S. Pat. No. 6,039,580, issued Mar. 21, 2000, entitled “RF CONNECTOR HAVING A COMPLIANT CONTACT”, U.S. Pat. No. 4,924,918, issued May 15, 1990, entitled “MACHINE FOR MANUFACTURING BUTTON CONNECTOR AND METHOD THEREFOR”, and U.S. Pat. No. 5,007,843, issued Apr. 16, 1991, entitled “HIGH-DENSITY CONTACT AREA ELECTRICAL CONNECTORS”, all of which are hereby incorporated by reference in their entirety into the present specification. Although the present invention described herein is described with respect to fuzz buttons, it should be understood that fuzz buttons are an illustrative type of conductive element or contact and that other types of electrically conductive elements or springs can be used with the present invention. The conductive element provides high reliability, multiple points of contact and is randomly compressed into a shape that provides multiple electrical contact points to a mating surface.  
         [0072]    The conductive element may take various suitable forms. As one example, the conductive element includes a “watch band” or POGO” pin, comprising at least one spring-loaded pin capable of being compressed. In a further alternative, the conductive element includes a bellows device comprising a plurality of deformable folds which are compressible. A further suitable conductive element includes a fuzz button which comprises a conductor formed into a plug-shaped compressible mesh. Alternatively, the conductive element may include belleville washers or an element comprised of an elastomer loaded with conductive particles. Preferably, the conductive element is plated with gold in order to ensure low, stable RF losses in benign or adverse environments.  
         [0073]    The conductive element may comprise a single element of one of the above-described, or other types suitable for providing at least one compliant end or, alternatively, may comprise more than one element, in which case at least one of the elements has at least one compliant end.  
         [0074]    Although the present invention is illustrated with respect to a right angle connector  18 , it should be understood that the present invention is equally usable in other configurations, for example, such as straight configurations between parallel circuit boards. Also, although the use of the present invention is discussed with respect to daughtercards and backpanels, this is only done for convenience and it should be understood that the electrical connector according to the present invention is usable for connecting all types of circuit boards as well as in other high speed applications.  
         [0075]    As illustrated in FIGS. 1A and 1B, the connector  18  would be assembled by connecting interposer  30  and the backpanel interposer  32 . As depicted in FIG. 1B, the connector  18  is assembled as follows. First, the twinax cables  40 ,  42  are formed. All of the fuzz buttons are installed into interposers  30 ,  32 . The twinax cables  40 ,  42  are then installed into the interposers  30 ,  32 . The assembly is then insert molded to form the over-mold  34  which makes the entire electrical connector  18  rigid. The over-mold  34  is preferably PBT. The electrical connector  18  could then be connected to the daughtercard  20  using fasteners such as screws, rivets, compression posts, and the like.  
         [0076]    The fuzz buttons  50 ,  52 ,  60 ,  62  can be made from a single gold plated fine wire that is compressed into a very small shape. The resulting object is a wire mass having spring performance and demonstrates superior electrical signal conduction from high current DC to microwave frequencies. The typical size of a fuzz button is 0.01 inch in diameter by 0.060 in length. The signal carrying fuzz buttons preferably have the same outer diameter as the signal carrying center cable. The ground contact fuzz buttons do not have to be the same diameter or length as the signal carrying fuzz buttons. The fuzz buttons  50 ,  52 ,  60 ,  62  are employed in the illustrative embodiments, preferably each formed from a strand of metal wire, each strand being wadded together to form a desired cylindrically shaped “button” of material having a density of between 20% and 30%. As depicted in FIGS. 1A and 1B, each wadded-wire connected fuzz button fits snuggly in openings of the daughtercard interposer  30  and the backpanel interposer  32 . The wadded-wire fuzz buttons  50 ,  52 ,  60 ,  62  make electrical contact at multiple points when compressed against the contact area. Connectors of this type have significant advantages over other types of connectors and provide connections of high integrity and reliability. In contrast to other types of connections, this mechanical connector element has very few associated variables that can affect the quality of the connection. The only significant variables are the size of the connector element and the compressive force used to make the connection, both of which can be accurately controlled by controlling the volume into which the fuzz button is placed. Alternatively, in high vibration environments, the fuzz buttons can be epoxied in place using a conductive epoxy.  
         [0077]    The fuzz buttons employed in the illustrative embodiments can be fabricated using nickel wire, or wire made from alloys such as beryllium and copper, silver and copper, or phosphorous and bronze. The compression of the wadded wire of fuzz buttons is substantially elastic so that, when the compressive force of the twinax cables is removed, the fuzz buttons return to their original shape. The wire is randomly compressed into a cylindrical shape and the wire has some spring constant associated with it to provide resiliency when pressure is applied. Advantageously, this allows the electrical connector  18  according to the present invention to be connected and disconnected as many times as is needed. In the embodiments described the wadded-wire connector elements  50 ,  52 ,  60 ,  62  can be manufactured by Technical Wire Products, Inc. of Piscataway, N.J., under the trademark Fuzz Button™.  
         [0078]    Referring now to FIG. 2, the twinax cables  40 ,  42  are inserted into the backpanel interposer  32 . FIG. 2 differs from FIG. 1 in that two twinax cables  40 ,  42  are depicted instead of one. It is important to note that central conductors  120 ,  122  are not shielded from each other. However, it is important to shield twinax pairs from each other as depicted in FIG. 2.  
         [0079]    As depicted in FIG. 2, the backpanel interposer  32  has two opposed U-shaped openings  100 ,  102  each having an outer U-shaped peripheral wall  110 ,  112 , respectively, an inner U-shaped peripheral wall  117 ,  118  and a straight wall  114 ,  116 , respectively. Walls  114  and  116  face each other as depicted in FIG. 2. Inserted into the U-shaped openings are a plurality of fuzz buttons  200 ,  202 ,  204 ,  206 , respectively, each being in a half U-shape as depicted in FIG. 2. For example, fuzz buttons  200 ,  202  each have a half U-shape and when placed together form a U partially surrounding the twinax cable  40 . It should be understood that other shielding methods could be used to replace the fuzz buttons.  
         [0080]    The twinax cable  40  has two central conductors  120 ,  122  surrounded by a Teflon™ sheathing  124 . Preferably, signal carrying fuzz buttons  300 - 306  (see FIG. 3) have the same outer diameters as the two central conductors  120 ,  122 . The Teflon™ sheathing  124  in turn is surrounded by an electrically conductive copper layer which forms a rigid or semi-rigid outer case  128  made of copper and aluminum or a tin filled braiding. Case  128  may be applied using a plating process. As depicted in FIG. 2, the rigid outer case  128  is stripped away to a length E, thereby exposing the Teflon™ sheathing  124 . The Teflon™ sheathing  124  is stripped away from the central conductor to a length F. This stripping is done symmetrically on both ends of twinax cables  40 ,  42 . The fuzz buttons  200 ,  202 ,  204 ,  206  are in electrical contact with the layer  128  so as to form a shield.  
         [0081]    Refer now to FIG. 3 which depicts a bottom view of FIG. 2. Mounted within the interposer  32  are fuzz buttons stacked one upon another in a half U-configuration through the thickness of interposer  32  for surrounding and shielding the central twinax leads  120 ,  122 , respectively, of twinax cables  40 ,  42 . Also depicted are a plurality of vertically extending cylindrical fuzz buttons  210 ,  212 ,  214  which are positioned between walls  114 ,  116 . The fuzz buttons  210 ,  214  extend through the thickness of interposer  32  and are used to shield twinax cables  40 ,  42  from each other. As depicted in FIG. 3, it should be understood that there is a full 360° shielding for twinax cables  40 ,  42  for the stripped away portions of coax cables  40 ,  42  which extend through the interposer  32 . As depicted in FIG. 3, there are four fuzz buttons  300 ,  302 ,  304 ,  306  are in contact with the exposed portions of central conductors  120 ,  122  of twinax cables  40 ,  42 .  
         [0082]    [0082]FIG. 4 is an illustration similar to FIGS. 2 and 3 in which the daughtercard interposer  32  has been omitted for clarity. As is evident in FIG. 4, there are four stacks of half U-shaped fuzz buttons  200 ,  222 ,  224 ,  226 ,  228 ;  202 ,  232 ,  234 ,  236 ,  238 ; and  204 ,  242 ,  244 ,  246 ,  248 ,  206 ,  252 ,  254 ,  256 ,  258  (not shown). These four stacks together with the vertically extending fuzz buttons form a full 360° shield around twinax cables  40 ,  42 . It is envisioned that the uppermost and lowermost fuzz buttons will be used in the present invention. However, it is possible to use structures other than fuzz buttons to electrically connect the uppermost and the lowermost fuzz buttons. For example, a stamped and formed metal component (not shown) can be used to electrically connect the uppermost and the lowermost fuzz buttons.  
         [0083]    Refer now to FIG. 5 which is similar to FIG. 4 except that fuzz buttons  200 ,  222 ,  224 ,  226  and  228  have been omitted to show fuzz buttons  306 ,  304  in contact with central conductors  122 ,  120 , respectively.  
         [0084]    As depicted in FIG. 6, it can be seen that fuzz buttons  300 ,  302  and also  304 ,  306  (not shown) contact the exposed portions of the central signal carriers  120 ,  122 . These fuzz buttons  300 - 306  are the signal carrying fuzz buttons. It is important that the signal carrying fuzz buttons are substantially the same diameter as the twinax central conductors  120 ,  122  to maintain constant impedance. It is also envisioned that other types of spring contacts could be used in the present invention. For example, conductive textiles may be used. Compression springs could also be used. The conductive textile may be injected into the connector replacing the fuzz buttons.  
         [0085]    Refer now to FIG. 7 where a bottom perspective view of the electrical connector  18  is depicted. As depicted in FIG. 7, a central portion  701  is formed between the straight wall  114  and the bottom of the outer U-shaped wall  110 . The central portion  701  includes through holes  700  and  702  which receive vertically extending fuzz buttons  300 ,  302 . A wall  704  is formed centrally in the U-shaped area to form a first half U-shaped opening  710  and a second U-shaped opening  712  which receive fuzz buttons  206 ,  252 ,  254 ,  256 ,  258  and  204 ,  242 ,  244 ,  246 ,  248 , respectively. It is envisioned that there could be a two piece construction and the center support structure could be a separate member constructed of a Teflon™ dielectric. Also, metal plated plastic components could be used.  
         [0086]    As depicted in FIG. 8, a plurality of electrically non-conductive patterns  402 ,  404  are on the daughtercard  20  and the backpanel  22 , respectively. The pattern  402  has an electrically conductive area  410  having roughly a figure eight configuration. The patterns can be formed using known photolithographic techniques. A first non-conductive area  412  and a second non-conductive area  414  are spaced apart from each and within an outer periphery  420  of the pattern  402 . The first non-conductive area  412  has two areas  430 ,  432  which include conductive pads  440 ,  442 . The second non-conductive area  414  has two areas  434 ,  436  which include conductive pads  444 ,  446 . Openings  430 ,  432 ,  434 ,  436  receive the center conductors  120 ,  122  of twinax cables  40 ,  42  that extend from the interposer  30  such that fuzz buttons  300 ,  302 ,  304 ,  306  are brought into contact with the conductive pads  440 ,  442 ,  444 ,  446 , respectively. Referring back to FIG. 4, fuzz buttons  228 ,  238 ,  248  and  258  will be in electrical contact with the electrically conductive area  410 . In this manner, the fuzz buttons provide a shielding path to ground. The electrically conductive area  410  is connected to ground plane on the daughtercard and on the backplane. The inner surfaces of openings  430 ,  432 ,  434 ,  436  are electrically conductive and are connected to signal paths so that fuzz buttons  306 ,  304 ,  302 ,  300  are in electrical contact therewith when the interposer  30  is used to connect the daughtercard  20  and the backpanel  22 . Fuzz buttons are mounted in the interposer  32  Advantageously, the fuzz buttons  300 ,  302 ,  304 ,  306  will be compressed when the daughtercard and backpanel are mated which provides a normal force on the signal line and on the cable. The fuzz buttons  300 ,  302 ,  304 ,  306  and  228 ,  238 ,  248 ,  258  will be compressed to the board  20  maintaining normal forces with respect to the daughtercard pattern  402 . The pattern  404  on the backpanel  22  is the same as the pattern  402  and need not be described in detail herein. The pattern  404  includes an electrically conductive portion  458  and a first non-conductive area  460  and a second non-conductive area  462 . Advantageously, the electrical connector  18  of the present invention can be connected and reconnected multiple times without degrading the signal contacts  300 ,  302 .  
         [0087]    It should be appreciated that the present invention is usable not only in daughtercard and backpanel or midplane applications but also in vertical motherboards, parallel boards, and cable link connections. It should also be understood that the present invention could also utilize fiber optic connectors to provide simultaneous optical and electrical signals to be transferred through the connector.  
         [0088]    Refer now to FIG. 9 where a backpanel  700  is depicted connected to a daughtercard  710 . The present invention is also usable in mid-plane connectors such as mid-plane connector  600  depicted in FIG. 9 which is connected to a daughtercard  610 .  
         [0089]    Refer now to FIG. 10 illustrating a second embodiment of an electrical connector  1000  according to the principles of the present invention. At the outset it should be noted that the electrical conductors  1020 ,  1022 ,  1024  have the same electrical characteristics as electrical conductors as  40 ,  42  illustrated with respect to the first embodiment. As depicted in FIG. 10, electrical conductor  1024  has the shortest path and electrical conductor  1020  has the longest path. Referring to FIG. 11, for example, conductor  1020  has a downwardly extending straight portion  1020 ′, an angled portion  1020 ″ and a horizontally extending straight portion  1020 ′″. The straight portions  1020 ′ and  1020 ″ facilitate installation of ends of the conductor  1020  into cable housing interposers  1030 ,  1032 , as explained below. For ease of explanation, only the housing for conductors  1020 ,  1022 ,  1024  is explained here, although other sets of conductors are illustrated which have the same housings. FIGS.  11 - 14  illustrate additional details of the second embodiment of the present invention.  
         [0090]    Referring again to FIG. 10, the electrical connector  1000  includes opposed guide blocks  1002 ,  1004  mounted on opposite ends of the electrical connector  1000 , as discussed in detail below. The guide blocks  1002 ,  1004  and the cable housings  1006 - 1014  can either be formed of individual molded parts as depicted and assembled together or can be formed as an over-molded assembly as described previously with respect to FIG. 1B. In between guide blocks  1002 ,  1004  are a plurality of sets of electrical conductors. As used herein, conductors  1020 ,  1022 ,  1024  form one vertical set of conductors. As illustrated in FIG. 10 there are four horizontal sets of three vertically stacked electrical conductors forming a vertical and horizontal array of twinax cable conductors, although it should be appreciated that any number of electrical conductors could be used in the present invention. For example, instead of four sets of conductors, there could be eight sets of conductors. Alternatively, there could be, instead of a stack of three conductors, there could be stacks of two conductors or four or five conductors depending on the application.  
         [0091]    Each of the electrical conductors  1020 ,  1022 ,  1024  are retained by cable housings  1006 ,  1008  and the other electrical conductors are retained by the respective cable housings  1008 - 1014 . As depicted in FIG. 10, cable housing  1006  is specially adapted to mate with the guide block  1002  using horizontal pins  1006 ′,  1006 ″ and  1006 ′″ which interlock with corresponding holes  1002 ′,  1002 ″ and  1002 ′″ in the guide block  1002 . Housings  1006 ,  1008  each include recesses  1007 ,  1009 ,  1011  and  1013 ,  1015 ,  1017 , respectively. Each cable housing includes a boss and a hole, for example, in cable housing  1008 , there is a boss  1023  and a hole  1025  for interlocking with the cable housing  1006 .  
         [0092]    As depicted in FIG. 10, the electrical connector  1000  is a right angle 90 degree electrical connector, although other configurations such as a straight connector can be arranged according to the present invention.  
         [0093]    The electrical connector  1000  includes a central twinax or coax portion  1001  which includes all of the copper wire conductors  1020 ,  1022 ,  1024  and all of the interlocked cable housings  1006 - 1012 , and the guide blocks  1002 ,  1004 . As depicted in FIG. 10, there is a front rectangular surface  1026  and a bottom rectangular surface  1028  to the assembled central assembly  1001 . Opposite ends of the conductors  1020 ,  1022 ,  1024  extend slightly beyond the surfaces  1026 ,  1028 , respectively, exposing the outer jacket  128  of each of the twinax conductors  1020 ,  1024 . The central conductors  120 ,  122  extend slightly beyond the dielectric  124  and the outer jacket  128  of the twinax conductors  1020 ,  1024 .  
         [0094]    A rectangular interposer  1030  has a front surface  1030 ′ and a back surface  1030 ″. The interposer  1030  mates (surface  1030 ′) with the front surface  1026  of assembly  1001 . A second rectangular interposer  1032  having a front surface  1032 ′ and a back surface  1032 ″ mates (surface  1032 ′) with the bottom surface  1028  of assembly  1001 . The copper wire conductors  120 ,  122  engage with the interposers  1030 ,  1032  as explained below.  
         [0095]    A plurality of fuzz buttons  1034 ,  1036  are retained by Mylar retainers  1038 ,  1040 , respectively. The Mylar retainers  1038 ,  1040  could be made from any suitable material including heat shrinkable plastic. The fuzz buttons  1034 ,  1036  are strategically placed and extend within interposer cable housing  1030 ,  1032  and interposer slides  1042 ,  1044 , respectively. The front surface  1030 ′ of the interposer  1030  is rigidly mounted to the front surface  1026  by either press fit studs, ultrasonic welding or epoxy. A pair of opposed pins  1009 ,  1009 ′ extend from the surface  1026  and the guide blocks  1002 ,  1004 , respectively, into recessed holes which (not shown) extend inwardly from the surface  1030 ′. The pins  1009 ,  1009 ′ keep the interposer  1030  aligned with the cable housings  1006 - 1014 . Pins (not shown) extend from the surface  1026  of the guide blocks  1002 ,  1004  to keep the interposer  1032  aligned with the cable housings  1006 - 1014 . The fuzz buttons  1034 ,  1036  include ground contact fuzz buttons and signal carrying fuzz buttons as explained below. A pair of guide pins  1046 ,  1048  are provided on the backpanel for mounting the electrical connector  1000  thereto. Guide pins  1046 ,  1048  extend through holes  1050 ,  1035  and  1048 ,  1033 , respectively, and mate with the latching mechanisms described below. As depicted in FIG. 10, a cylindrical guide socket body  1003  extends from the guide block  1002  for receiving the guide pin  1048 . Guide block  1004  has a similar guide socket body (not shown) for receiving guide pin  1046 . The guide blocks  1002 ,  1004  each have a threaded insert  1027 ,  1029 , respectively, positioned at right angles from the guide socket body  1003  and aligned with corresponding holes  1061 ,  1063  in interposer  1030  and holes  1080 ,  1082  in the interposer slide  1042 . Threaded fasteners extend from the daughtercard to fasten the electrical connector  1000  to be threaded into the threaded inserts  1027 ,  1029 .  
         [0096]    Turning now to FIG. 11, it can be more clearly seen that the mylar sheet  1038  includes a plurality of stamped holes. The stamped holes are in a specific pattern for retaining and placing the fuzz buttons in holes in the interposers  1030 ,  1032  and the interposer slides  1042 ,  1044 . The holes used to retain the signal carrying fuzz buttons must be held to tight tolerances to hold the fuzz buttons securely yet not so tight to overly compress the fuzz buttons and significantly change the outer diameter thereof.  
         [0097]    Stamped holes  1070 ,  1072 ,  1074  and  1076  are in vertical alignment for receiving retaining tines  1090 ,  1092 ,  1094 ,  1096  in the interposer  1030 . The holes  1404 ,  1406  and the retaining tines  1090 - 1096  maintain the interposer slide  1042  in alignment with the interposer  1030 . The retaining tines  1090 - 1096  are of sufficient length to permit the interposer slide  1042  to be biased into the extended position by springs  1091 ,  1093  mounted in holes  1095 ,  1097  in the surface  1030 ″ of the interposer  1030 . The retaining tines  1090 - 1096  will be flush or below surface  1092  in the retracted position. The fuzz buttons  1034  maintain the alignment of the Mylar sheet  1038  relative to the interposer  1030  and the interposer slide  1042 . The interposer  1030  includes a top set of holes  1110  for receiving the leads of conductor  1020 , middle holes  1112  for receiving the center leads of conductor  1022  and a bottom set of holes  1114  for receiving the leads of the conductor  1024 . Each interposer has multiple ground holes, for example, four ground holes, into which fuzz buttons are placed to make contact with the outer conductive layer  128  of each of the conductors  1020 ,  1022 ,  1024 . For example, as depicted in FIG. 11 with respect to conductor  1020 , the interposer  1030  has holes  1120 ,  1122 ,  1124 ,  1126 . The mylar sheet has corresponding holes  1130 ,  1132 ,  1134 ,  1136 . Each interposer  1030 ,  1032  includes a plurality of recesses shaped to match the exterior of each of the conductors  1020 ,  1022 ,  1024 . As depicted in FIGS. 11 and 12, the electrical conductors have a straight center section and rounded outer sections. The fuzz buttons placed in holes  1130 ,  1132 ,  1134 ,  1136  will be in contact with the outer jacket  128  of the conductor and will provide a ground path and electrical shield between adjacent twinax cables. The recess  1150  extends inwardly from front surface  1032 ′ of the interposer  1032 . For example, the recess  1150  is formed by opposed curved walls  1160 ,  1162  connected by straight sections  1170 ,  1172 . The straight sections  1170 ,  1172 , as depicted extend horizontally. The recess  1150  is shaped to receive the outer jacket  128  of the twinax cable.  
         [0098]    Turning now to FIG. 12, the interposer  1032  is depicted in large data. It should be understood that interposers  1030 ,  1032  are identical except for the opposed holes used for the guide pins  1046 ,  1048  which extend through interposer  1032  into guide blocks  1002 ,  1004 , respectively. The holes  1048 ,  1050  are offset relative to a longitudinal centerline of the interposer slide  1044  as are holes  1033 ,  1035  which are aligned therewith. By contrast, the holes  1066 ,  1068  in the interposer  1030  are on the centerline as are the holes in the interposer slide  1048 .  
         [0099]    Each central conductor  120 ,  122  has multiple fuzz buttons associated with it. For example, as depicted in FIG. 12, there are two holes  1260 ,  1262  aligned with the central conductors  120 ,  122 . There are also two central fuzz buttons (not shown) which make contact with the central leads of the conductors  120 ,  122  and which have one end in the holes  1260 ,  1262 . A front surface of the insulator  124  can bottom out in the recess  1150 . With respect to the recess  1150 , there are four fuzz buttons  1250 ,  1252 ,  1254 ,  1256  installed in holes  1280 - 1284 . Holes  1280 - 1284  are blind holes and intersect with the periphery of the recess  1150 . One ground contact, preferably a fuzz button (not shown) is installed in the holes  1250 - 1256  and are used as ground contacts with the electrically conductive outer jacket  128  of the central conductor. Four ground contacts provide excellent shielding. Additional holes and fuzz buttons can be added to enhance cross-talk reduction.  
         [0100]    It should be noted that hole  1250  is centrally located between signal carrying fuzz buttons  1260 ,  1262 . Hole  1254  is offset relative to the center of recess  1150  closer to hole  1260 , whereas in the adjoining recess  1152 , hole  1270  is offset in the opposite direction. It should be noted that excellent electrical shielding is achieved without having to provide 360 degree coverage of each of the twinax cables. Thus, adjacent vertically aligned recesses have offset holes for fuzz buttons. By offsetting the holes, a greater percentage of the circumference is shielded.  
         [0101]    Referring now to FIGS. 13A, B and C and referring to the interposer slide  1042 , it should be seen that there are four vertically aligned holes  1370 ,  1372 ,  1374 ,  1376  for receiving tines  1090 ,  1092 ,  1094 ,  1096 , respectively. Preferably, the interposer will be spring loaded in a direction away from interposer  1030 . This protects the fuzz buttons from becoming damaged or dislodged during shipping and assembly. It should be understood that the explanation is provided only for the left most set of holes and that the hole pattern repeats. The upper most conductor  1020  has a set of corresponding holes in the interposer  1042 . Hole  1330  for receiving a ground fuzz button aligns with hole  1130  in the mylar sheet and hole  1120  in interposer  1030 . Hole  1332  aligns with hole  1132  in the mylar sheet and hole  1122  in the interposer. Hole  1334  aligns with hole  1134  in the mylar sheet and hole  1124  in the interposer  1030 . Hole  1336  aligns with hole  1136  in the mylar sheet and hole  1126  in interposer  1030 . Similarly, holes  1380  align with holes  1080  in the mylar sheet  1038  and holes  1110  in the interposer  1030 . As depicted in FIG. 13A, the interposer  1032  is illustrated in an extended position in which the fuzz buttons are below the surface  1042 ″ or at maximum 0.020 above the surface  1042 ″ and are thereby protected during shipment of the electrical conductor  1000 . As depicted in FIG. 13A, there is a gap between the surface  1032 ″ of the interposer  1032  and the surface  1042  of the interposer slide. The fuzz buttons are held between the interposer  1030  and the interposer slide  1048  are in contact with the daughtercard  20 . By contrast, the interposer  1032  and the interposer slide  1044  are in contact with the backpanel  22 .  
         [0102]    The backpanel printed circuit board with guide has a plurality of conductive pads  1390 . The pads have two signal carrying conductors  1392 ,  1394  to be brought into contact with the signal carrying fuzz buttons and an outer ground section  1396  (see FIG. 14). The pads  1390  advantageously do not have to be through plated holes. The pads  1390  can be surface mount or can have blind vias. By avoiding through plated holes, capacitive effects associated with the holes are reduced and speed can be increased.  
         [0103]    It is important to provide shielding for the length of the exposed central conductor and for the length of the signal carrying fuzz buttons to prevent cross-talk between adjacent twinax cables. The present invention advantageously achieves this shielding using four fuzz buttons connected to ground. These fuzz buttons provide less than 360° shielding but testing has revealed that the level of shielding achieved is sufficient to provide data rates up to 10 Gb/sec and greater.  
         [0104]    Further, the Mylar sheet  1038  retains the signal carrying fuzz buttons by compressing the fuzz button around the circumference without reducing the outer diameter significantly. Thus, the diameter of the fuzz button is not changed significantly when compressed into the PC board. Also advantageously, the force exerted by the fuzz button in a direction away from the PC board is relatively small thus allowing the use of the latching mechanism according to the present invention. By changing the shape, number and rigidity of the conducting elements, the contact resistance, contact force and compressibility can be selected within a wide range to meet the needs of the particular application. The overall cumulative contact force of buzz buttons  1039 ,  1036  against contact surfaces  1390  is low due to the resilient construction and compressibility of the buttons.  
         [0105]    Because the electrical connector according to the present invention is a compression mount-type, a unique latching device is preferably used with the electrical connector depicted in FIGS.  10 - 14 . To ensure a good electrical connection, between the fuzz buttons and the PC board pads, the daughtercards must not be able to back out of its position in the slot beyond a predetermined distance. This predetermined distance is calculated to ensure the minimum amount of normal force required for an acceptable electrical connection. The latching device can advantageously be used with all compression mount type connectors and is not limited to the compression type connector described herein. A connector guidance module is used as device for maintaining a latched position for an interconnect system. The latching device maintains intimate contact between compression mount contacts (fuzz buttons) and the PC board surface without using additional fasteners. The latching device will operate very similarly to a quick disconnect hose fitting, but will not necessarily have a positive lock requiring more than just enough force to disengage the latch device. The spring members and guide pin shape are designed for mating of the latching device with a minimum of force into a latched position. A groove in the guide pin and the latching device are designed to require more force to separate than the force generated by he compression contacts against the PC board in a direction to force the latching into an unlatched position.  
         [0106]    Other arrangements for the latching mechanism would include but are not limited to replacing the spring members shown with another type of spring, such as a (garter spring) extension coil as depicted in FIG. 26. The latching devices shown here have a cylindrical cross-section may be replaced with spherical ball component. The “groove” in the guide pin is shown here as having a shape to closely match the latching devices&#39; shape, but may be replaced with a simple “V” groove and/or for retention “U” groove.  
         [0107]    Referring now to FIG. 15, a latching guide module  1500  is depicted in an exploded perspective view. The latching guide module is especially useful when used in combination with the second embodiment depicted in FIGS. 1014. As depicted in FIG. 15, there is a housing or guide block  1002  and a cable housing block  1006 . Housing  1002  and housing  1006  each have a portion or half of a through bore  1502 ,  1504 , respectively. A guide socket body  1510  is mounted within the bore formed by  1502 ,  1504  and is retained therein as discussed in detail below.  
         [0108]    Each housing  1502 ,  1504  has a slot  1512  and  1514  (not shown). The slots  1512 ,  1514  are transverse relative to the through bore. The guide socket body has three spaced circumferential arcuate slots  1532  (not shown)  1534  and  1536  spaced by walls  1533 ,  1535 ,  1537 , respectively. The latching devices  1522 ,  1524 ,  1526  fit into slots  1532 ,  1534 ,  1536 , respectively. The latching devices  1522 - 1526  each have an annular arcuate shape with an inner surface  1522 ′- 1526 ′ and an outer surface  1522 ″- 1526 ″. The guide pin  1048  has an outer cylindrical surface  1550  and an annular groove  1552 . The groove  1552  has two opposed angled sections  1572 ,  1574  and a straight section  1576  connecting the angled sections  1572 ,  1574 . The inner surfaces  1522 ′- 1526 ′ are shaped to match the shape of the annular groove  1552 . Three arcuate shaped leaf spring members  1562 ,  1564  and  1566  are mounted within grooves  1512 ,  1514  and are in contact with latching devices  1522 ,  1524 ,  1526 , respectively. The guide socket body  1510  is retained in the through bore by a combination of three latching devices  1522 ,  1524 ,  1526  and the springs  1652 ,  1564 ,  1566  which bias the latching devices inwardly.  
         [0109]    Each of the twinax cable embodiments is particularly suitable for differential signaling. A driver on one board sends out two signals and at the receiving board, the difference between the two signals is measured and the actual signal pulse is determined. Because the two conductors are shielded from adjacent twinax cables by the conductive jacket, the twinax cable is especially useful for differential signaling. With a differential pair each signal is transmitted on two lines  140 ,  142  at the same time. On one, the signal is transmitted as a positive (+) signal, on the other as a Negative (−) signal. At the receiving end of the signal path the receiver device gets two signals. Both signals, however, have been changed by the noise that penetrated through the outer jacket  128  and through the fuzz button shielding over the signal path. The changes came in the form of unwanted voltage added to the wanted signal. At this point it is important to note that the unwanted voltage got added to both lines at the same time and by the same amount. The essence of the differential system is that the receiver is designed to take the difference between the two signals on the two lines. In doing that, the noise part of the signal, equal on both lines, gets eliminated and what remains is clear signal. As indicated above, the differential system works well if the noise added is equal on the two lines, i.e., the positive (+) and the negative (−). To ensure that the noise hits both of these lines identically, both of them need to occupy theoretically the same physical space. This is true in the present invention in which the two physical lines are within the twinax cable structure.  
         [0110]    Referring now to FIG. 16, the electrical connector  1000  is shown engaged with the daughtercard  20 . The interposer slide  1042  is depicted in a retracted engaged position. The interposer slide  1044  is shown in an extended non-engaged position. The mylar sheet  1038  is in contact with the surface  1030 ″. When interposer slide  1044  engages with the top surface of the backpanel  22 , the interposer slide  1044  will slide inwardly to a retracted engaged position. The latching mechanism will engage with the grooves  1552  of pins  1501 ,  1503  such that all of the fuzz buttons will be in proper contact with the daughtercard and backpanel pads. This is depicted in FIG. 17 where the electrical connector  1000  is connected to the daughtercard  20  and the backpanel  22 .  
         [0111]    Turning now to FIG. 18, the guide module is depicted in a fully mated state, with one half of the housing removed to better expose the latching mechanism. The springs  1564 - 1566  and the latching devices  1564 ,  1566  are shown in a normal latched engaged position. The springs  1562 - 1566  bias the latching devices into the groove  1552 .  
         [0112]    [0112]FIG. 19 depicts the guide module with the latching mechanism in the normal unmated condition.  
         [0113]    [0113]FIG. 20 depicts the guide module, in a partially mated condition, with one half of the housing removed and the guide socket  1510  omitted to expose the latching mechanism. This illustrates how the springs and latching devices operate during the mating process. In FIG. 20, the spring members  1562 - 1566  bias the latching devices  1522 - 1526  inwardly. In the partially mated condition the inner surfaces  1522 ′- 1526 ′ are in contact with cylindrical surface  1558  of the guide pin  1550 . When the guide pin  1510  engages the latching devices  1522 - 1526 , the latching devices  1522 - 1526  are biased radially inwardly as depicted in FIG. 23 and the latching devices  1522 - 1526  extend inwardly past the slots  1512 - 1516  such that the inner surfaces  1522 ′- 1526 ′ engage the groove  1552 . The guide pin  1501  has a tapered top section  1558  to facilitate engagement with the latching devices  1522 - 1526 . The insertion force overcomes the spring bias exerted by spring members  1562 - 1566  such that the latching devices  1522 - 1526  move radially outwardly until the latching devices are biased inwardly into the grooves  1552 . Advantageously, the force exerted by the springs  1562 - 1566  is sufficient to maintain force on the fizz buttons to keep the fuzz buttons engaged with the pads. However, there is no positive lock using this latching device but merely a friction fit sufficient to hold the electrical connector in place against the daughtercard.  
         [0114]    [0114]FIG. 21 depicts the guide module, in a top view with the guide pin  1501  in the fully installed position. In FIG. 21, the grooves  1512 ,  1514  are illustrated in a top view. Together slots  1512 ,  1514  from a hexagonal shape have walls  2102 ,  2104 ,  2106 ,  2108 ,  2110  and  2112 . In FIG. 21, springs  1562 ,  1564 ,  1566  are engaged with walls  2104 ,  2108 ,  2112  respectively. As depicted in FIGS.  1525 , there are three latching devices and springs depicted, although any number can be used. As depicted in FIGS.  15 - 25 , the latching devices and springs are separated by 120°.  
         [0115]    [0115]FIG. 22 illustrates the latching devices in the normal position.  
         [0116]    [0116]FIG. 23 is the same as FIG. 22 with the guide socket in place with the latching devices in the “closed position”.  
         [0117]    [0117]FIG. 24 is a view from the same direction as in FIGS.  21 - 23 . It illustrates the latching devices in the full “open” position during the mating cycle.  
         [0118]    [0118]FIG. 25 is a perspective view with the guide pin engaged with a latching device and the cable housing and some latching devices and springs omitted for clarity.  
         [0119]    Advantageously, the spring members  1562 - 1566  and latching devices  1522 - 1526  and the shape of the guide pin are designed to mate electrical connector to the backpanel  22  with a minimum of force. The groove  1552  and the guide pin  1501  and the springs  1562 - 1566  are designed to require more force to separate the components than the force generated by the compression contacts against the PC board. Other options for construction can be accomplished using spring members with another type of spring such as a garter spring (extension coil). The latching devices shown and described have a cylindrical cross-section but the cylindrical cross-section may be replaced with a spherical ball component. The groove in the guide pin is shown as having a cliche closely matching the latching device shaved but may be replaced with a simple “V” groove for retention.  
         [0120]    As depicted in FIG. 26, the entire latching device can be replaced with a single garter spring  2602 . The garter spring  2602  is retained in grooves  1512 ,  1514  of blocks  1502 ,  1504 . The spring  2602  works similarly to the latching device described with respect to FIG. 15 but is considerably simpler in terms of assembly. During operation, the garter spring  2602  remains in the grooves  1512 ,  1514 . When the electrical connector is fully engaged with the guide pin  1048 , the garter spring  2602  will be retained in the annular groove  1552  thereby maintaining the electrical connector in a mated position with the printed circuit board.  
         [0121]    It is anticipated that the electrical connector according to the present invention can provide in the range of 80 twinax lines per linear inch in a 20 millimeter card slot. For radio frequency coaxial applications, this connector can be used in the single ended configuration at frequencies to 10 Gb/sec and higher. While these connectors have been described as advantageous to use in backplane systems these connectors also find applicability in many other applications where printed circuits are required to have high density electrical interconnects between adjacent printed circuit boards.  
         [0122]    It will be readily seen by one of ordinary skill in the art that the present invention fulfills all of the objects set forth above. After reading the foregoing specification, one of ordinary skill will be able to affect various changes, substitutions of equivalents and various other aspects of the invention as broadly disclosed herein. It is therefore intended that the protection granted hereon be limited only by the definition contained in the appended claims and equivalents thereof.