Abstract:
A connector assembly is provided having signal contacts and a ground plane mounted within a housing. The ground plane includes a plurality of spring contacts positioned along one edge and adapted to cooperatively engage a conductive edge surface of a printed circuit board ground plane without penetrating or extending into the edge of the printed circuit board.

Description:
[0001]    This application claims priority from co-pending provisional patent application Serial No. 60/259,602, filed Jan. 2, 2001. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The invention is generally related to electrical connectors which are mounted on a printed circuit board, and more particularly to an electrical connector which has surface mount terminals and resilient terminals which extend from a mating surface thereof.  
         BACKGROUND OF THE INVENTION  
         [0003]    Electrical connectors that are mounted to a printed circuit board are well known in the art. As the size of the electronic devices in which the printed circuit boards are installed has decreased, the density of the connectors positioned on those boards has increased. Such electronic devices also require electrical connectors with numerous terminals be mounted on a printed circuit board in such a manner as to occupy a minimal area of printed circuit board real estate.  
           [0004]    In order to provide for a higher density of connectors on printed circuit board, surface mount technology was utilized. With surface mounting, the conductive pads on the printed circuit board can be closely spaced, thereby allowing more contacts to be mounted in the same area of the board. As the density of the connectors on the printed circuit board increases, the length of the terminals cannot increase significantly without degrading the electrical performance of the electronic device. This is particularly true in electronic devices designed for high speed applications. Typically, high density connectors which have the shortest path over which the signals must travel operate optimally. As the density of interconnects increases, and the pitch between contacts approaches 0.5 mm or less, the close proximity of the terminal contacts increases the likelihood of strong electrical cross-talk coupling between the terminal contacts. In addition, maintaining design control over the electrical characteristic impedance of the terminal contacts becomes increasingly difficult.  
           [0005]    Modern electronics requires the use of high frequency and high speed connectors particularly for use in interconnecting circuitry on motherboards or backplanes and daughter cards or other circuit devices. These connectors require shielding or ground planes between the signal pins; e.g., stripline configuration, to provide high frequency signal integrity and minimize interference from outside sources. U.S. Pat. No. 4,975,084 discloses one such system provided with ground contacts between columns of signal contacts, the ground contacts of one connector having projecting blades and the mating ground contacts of the other connector including plates with cantilevered beams. The plates provide a shield between the columns of mated signal contacts and the cantilevered beams engage the blades to complete the ground circuits. The ground contacts of this connector are disposed within slots extending from the sidewall and partially across the respective housings and the connector includes an array of power, signal and ground contacts. This arrangement requires an amount of dielectric housing material to insulate between the adjacent contacts and to isolate the various circuits. For some applications, it is desirable to have a more highly dense array or grid of contact members, while maintaining the integrity between the lines. As the center line spacing between contact members in a row is decreased, the spacing between adjacent columns of contact members is likewise decreased, thereby necessarily reducing the amount of dielectric housing material between the members of the array. This in turn affects the electrical characteristics of the connector system and in particular reduces the impedance through the connector system. It is desirable, therefore, to have an electrical connector that provides a more dense array of contact members while maintaining the electrical characteristics associated with connectors having a less dense array of contact members.  
           [0006]    Though there are many types of connectors available, it would be desirable to have a connector with a precisely controlled impedance to reduce signal reflections. It would also be desirable to have a connector which could accommodate fast signals, those with rise times on the order of 250 psec or less. Such a connector should also be durable while at the same time being detachable so that printed circuit boards can be joined and separated during use.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention provides an electrical connection between an electrical connector and an edge surface of a substrate. In order to accomplish this, spring contacts are formed on or adjacent to a mating edge of an electrical ground plane portion of an electrical connector so as to be in position to electrically and mechanically engage the edge surface of the substrate, but without penetrating that edge surface. Thus in one embodiment, a connector assembly is provided that has signal contacts and a ground plane mounted within a housing. The ground plane includes a plurality of spring contacts positioned along one edge and arranged so as to electrically engage only a conductive edge surface of a printed circuit board ground plane.  
           [0008]    The invention is also directed to an electrical connector adapted to electrically engage a printed circuit board ground plane having a portion exposed at the edge surface of the printed circuit board and to a connector assembly. The connector assembly has a housing with first and second terminals. The first and second terminals have first and second mounting portions, respectively, which cooperate with a printed circuit board provided proximate the housing. The printed circuit board has conductive areas provided on top and bottom surfaces, and on at least one of the peripheral edge surfaces that extend between the top and bottom surfaces.  
           [0009]    The first terminals are secured in the housing, with first securing portions of the first terminals provided in first terminal receiving cavities. The first mounting portions are integral with the first securing portions and extend outside the housing, so as to allow the first mounting portions to cooperate with the conductive areas provided on the top and bottom surfaces of the printed circuit board. The second terminals are also secured in the housing, with second securing portions of the second terminals provided in second terminal receiving cavities. The second mounting portions are integral with the second securing portions and extend outside the housing, so as to allow the second mounting portions to cooperate with the at least one conductive area located on the peripheral edge surfaces that extend between the top and bottom surfaces.  
           [0010]    The at least one conductive area located on the peripheral edge surfaces of the printed circuit board is positioned proximate an edge surface of the printed circuit board. The second mounting portions comprise a biasable structure, e.g., a spring structure. The biasable structure cooperates with the edge surface of the substrate to allow the second mounting portions to electrically and mechanically engage the conductive area proximate to the edge surface of the substrate without projecting into or extending through an edge surface of the printed circuit board.  
           [0011]    An electrical circuit assembly is also provided that includes a printed circuit board having at least one conductive grounding plane positioned below opposing top and bottom surfaces. The at least one conductive grounding plane is constructed so as to electrically communicate with at least one conductive edge surface that is accessible at a peripheral edge surface of the printed circuit board that extends between the opposing top and bottom surfaces. A connector is assembled to the printed circuit baord that comprises signal contacts and a ground plane mounted within a housing. The ground plane of the connector includes a plurality of spring contacts positioned along one edge that are arranged so as to electrically engage the at least one conductive edge surface of the at least one conductive grounding plane of the printed circuit board. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    These and other features and advantages of the present invention will be more fully disclosed in, or rendered obvious by, the following detailed description of the preferred embodiment of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts and further wherein:  
         [0013]    [0013]FIG. 1 is a perspective view of a connector assembly formed in accordance with the present invention;  
         [0014]    [0014]FIG. 2 is an exploded perspective view of the connector assembly of FIG. 1, showing a first connector housing, a second connector housing, and a bus bar ground plane;  
         [0015]    [0015]FIG. 3 is a partial cross-sectional view of the connector housings shown in FIG. 2, the bus bar ground plane of FIG. 2 is positioned in the first connector housing;  
         [0016]    [0016]FIG. 4 is a partial cross-sectional view of the connector housings, similar to that shown in FIG. 3, with the connector housings mated together;  
         [0017]    [0017]FIG. 5 is a cross-sectional view of the connector housings prior to connector housings being mated with each other;  
         [0018]    [0018]FIG. 6 is a cross-sectional view of the connector housings, similar to that of FIG. 5, showing the connector housings in a mated condition;  
         [0019]    [0019]FIG. 7 is a cross-sectional view of the connector housings, taken in a different plane than the cross-sectional view of FIG. 6, showing the connector housings in a mated condition;  
         [0020]    [0020]FIG. 8 is a top perspective view of the first connector housing, before the first connector housing has been positioned on the edge of the first printed circuit board;  
         [0021]    [0021]FIG. 9 is a bottom perspective view of the first connector housing, before the first connector housing has been positioned on the edge of the first printed circuit board;  
         [0022]    [0022]FIG. 10 is a top perspective view of the second connector housing with terminals exploded therefrom, before the second connector housing has been positioned on the surface of the second printed circuit board;  
         [0023]    [0023]FIG. 11 is a bottom perspective view of the second connector housing, before the second connector housing has been positioned on the surface of the second printed circuit board; and  
         [0024]    FIGS.  12 - 15  are each a perspective, partially broken-away view of the first printed circuit board illustrating the positioning of alternative biasable members of a bus bar ground plane relative to the conductive edge surface of the first printed circuit board. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0025]    This description of preferred embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. The drawing figures are not necessarily to scale and certain features of the invention may be shown exaggerated in scale or in somewhat schematic form in the interest of clarity and conciseness. In the description, relative terms such as “horizontal,” “vertical,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing figure under discussion. These relative terms are for convenience of description and normally are not intended to require a particular orientation. Terms including “inwardly” versus “outwardly,” “longitudinal” versus “lateral” and the like are to be interpreted relative to one another or relative to an axis of elongation, or an axis or center of rotation, as appropriate. Terms attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. The term “operatively connected” is such an attachment, coupling or connection that allows the pertinent structures to operate as intended by virtue of that relationship. In the claims, means-plus-function clauses are intended to cover the structures described, suggested, or rendered obvious by the written description or drawings for performing the recited function, including not only structural equivalents but also equivalent structures.  
         [0026]    Referring to FIGS. 1 and 2, an electrical connector assembly  10  formed in accordance with the present invention provides electrical connection between a first circuit board  12  and a second circuit board  14 . Connector assembly  10  has a first connector housing  16  and a second connector housing  18 .  
         [0027]    More particularly, first connector housing  16  includes a first or mating surface  20  and an oppositely facing second or terminal receiving surface  22 . End walls  24  and side walls  26  extend between mating surface  20  and terminal receiving surface  22 . Side walls  26  have transition portions  28 , since mating surface  20  is larger than terminal receiving surface  22 . A mating connector receiving recess  30  extends from mating surface  20  toward terminal receiving surface  22 . Mating connector receiving recess  30  is dimensioned to be positioned proximate end walls  24  and proximate side walls  26 .  
         [0028]    Terminal receiving cavities  32  are provided in first connector housing  16  and extend from terminal receiving surface  22  to mating connector receiving recess  30 . As best shown in FIG. 5, terminal receiving cavities  32  are provided on both sides of the longitudinal axis of first connector housing  16 . Terminal receiving cavities  32 , that are provided on a respective side of the axis, are mirror images of the terminal receiving cavities provided on the opposite side of the axis. Referring to FIG. 5, terminal receiving cavities  32  have dividing walls  34  which separate the terminal receiving cavities into two portions, first leg receiving cavities  36  and second leg receiving cavities  38 . Dividing walls have lead-in surfaces  40 ,  42  which are provided proximate terminal receiving surface  22 . Shoulders  44  are provided on dividing walls  34  on surfaces of the dividing walls which are positioned proximate second leg receiving cavities  38 . Securing projections  46  are also provided in terminal receiving cavities  32 .  
         [0029]    Bus bar receiving recesses  48  (FIGS. 5 and 7) are provided in first connector housing  16 . Bus bar receiving recesses  48  extend from mating connector receiving recess to terminal receiving surface  22 . First connector terminals  50  (FIG. 50 have mounting portions  52 . First legs  54  and second legs  56  extend from mounting portions  52  in essentially the same direction, thereby enabling first and second legs  54 ,  56  to be mated with the mating connector. Printed circuit board mating legs  58  extend from mounting portions  52  in a direction which is opposed to first and second legs  54 ,  56 .  
         [0030]    Mounting portions  52  have recesses  60  provided on side surfaces. Recesses cooperate with securing projections  46  to provide the interference fit required to maintain terminals  50  in terminal receiving cavities  32 . It should be noted that end surfaces of dividing walls  34  also cooperate with surfaces of mounting portions  52  to ensure that terminals  50  are properly positioned. First legs  54  have a slightly arcuate configuration. Free ends of first legs have enlarged contact sections  62  which extend beyond first leg receiving cavities  36  and into mating connector receiving recess  30 . Enlarged positioning sections  64  are also provided on first legs  54 . Positioning sections  64  cooperate with dividing walls  34  when the first legs are in an unmated condition. It is important to note that first leg receiving cavities  36  are dimensioned to receive first legs  54 , thereby allowing the first legs to move from an unmated or slightly prestressed position to a mated position.  
         [0031]    Second legs  56  are positioned in second leg receiving cavities  38 . Unlike the first legs, second legs  56  do not extend into mating connector receiving recess  30 . Free ends  66  of second legs  56  are provided at an angle relative to the second legs. This allows the free ends  66  to engage dividing walls  34 . Lead-in surfaces  68  are provided at free ends  66  of second legs  56 .  
         [0032]    Bus bar ground planes  70  are positioned in first connector housing  16 . Bus bars  70  preferably have connector mating portions  72  and biasable structures  74  positioned along or adjacent to a free edge  75 . Connector mating portions  72  extend from receiving recesses  48  into mating connector receiving recess  30 . Biasable structures  74  may comprise various spring configurations (FIGS.  12 - 15 ) either formed integral with free edge  75  or fastened to bus bar  70  adjacent to free edge  75  so as to be engagable with a conductive side edge (shown generally at  220 ) of a printed circuit board. It will be understood that conductive side edge  220  extends between opposing top and bottom surfaces  212  so as to intersect surfaces  212 , but is not coplanar with surfaces  212 . Side edge  220  may be electroplated so as to present a generally flat, conductive surface for engagement with biasable structures  74 , but without biasable structures  74  entering the circuit board edge. Conductive side edge  220  is disposed and structurally arranged so as to be in electrical communication with conductive grounding planes  214  that are positioned below opposing top and bottom surfaces  212  (FIG. 3).  
         [0033]    Biasable structures  74  may comprise one or more cantilever, compression, or straight or canted coil springs that have been separately or integrally formed along free edge  75  of bus bar ground plane  70 , or may be a combination of compression spring and contact that are arranged on or adjacent to bus bar ground plane  70  so as to project outwardly from free edge  75  while being in electrical communication with bus bar ground plane  70 . Advantageously, biasable structures  74  resiliently cooperate with conductive edge surface  220  of the printed circuit board to provide electrical and mechanical engagement between bus bar ground plane  70  and conductive grounding planes  214  positioned below opposing top and bottom surfaces  212  and within the printed circuit board. It is significant to the invention that biasable structures  74  or free edge  75 , or any nonbiasable structures that engage conductive side surface  220  do so without projecting into or extending through the edge surface of the printed circuit board. It will be understood that nonbiasable means, e.g., a straight, non-protruding edge, or detents, nubs, protrusions or other raised or outwardly projecting structures, may be formed along free edge  75  which may be adequate for electrical and mechanical engagement between bus bar ground plane  70  and a ground plane positioned within the printed circuit board, without projecting into or extending through the edge surface of the printed circuit board.  
         [0034]    Second connector housing  18  includes a first or mating surface  120  and an oppositely facing second or terminal receiving surface  122 . End walls  124  and side walls  126  extend between mating surface  120  and terminal receiving surface  122 . A mating projection  130  extends from mating surface  120  away from terminal receiving surface  122 . Mating projection  130  is dimensioned to extend between end walls  124 . Terminal receiving cavities  132  are provided in second connector housing  18  and extend from terminal receiving surface  122  to mating surface  120 . Terminal receiving cavities  132  are provided on both sides of the longitudinal axis of second connector housing  18 . Terminal receiving cavities  132  provided on a respective side of the axis, are mirror images of terminal receiving cavities provided on opposite side of the axis.  
         [0035]    Referring to FIG. 5, terminal receiving cavities  132  have dividing walls  134  which separate the terminal receiving cavities into two portions, first leg receiving cavities  136  and second leg receiving cavities  138 . Dividing walls  134  have lead-in surfaces  140 ,  142  which are provided proximate terminal receiving surface  122 . Shoulders  144  are provided on dividing walls  134  on surfaces of dividing walls  134  which are positioned proximate second leg receiving cavities  138 . Securing projections  146  are also provided in terminal receiving cavities  132 . Bus bar receiving recess  148  second connector housing  18 . Bus bar receiving recess  148  extends from terminal receiving surface  122  past mating surface  120  through mating projection  130 . Second connector terminals  150  (FIG. 5) have mounting portions  152 . First legs  154  and second legs  156  extend from mounting portionsl 52  in essentially the same direction, thereby enabling first and second legs  154 , 156  to be mated with the mating connector. Printed circuit board mating legs  158  and stand off legs  159  extend from mounting portions  152  in a direction which is opposed to first and second legs  154 , 156 .  
         [0036]    Mounting portions  152  have recesses  160  provided on side surfaces. Recesses  160  cooperate with securing projections  146  to provide the interference fit required to maintain terminals  150  in terminal receiving cavities  132 . Terminals  150  have projections  161  which extend from side surfaces. Projections  161  facilitate the interference fit of the terminals. It should be noted that end surfaces of dividing walls  134  also cooperate with surfaces of mounting portions  152  to ensure that terminals  150  are properly positioned.  
         [0037]    First legs  154  have a slightly arcuate configuration. The free ends of the first legs have enlarged contact sections  162  which extend beyond first leg receiving cavities  136  and beyond mating surface  120 . Enlarged positioning sections  164  are also provided on the first legs  154 . The positioning sections  164  cooperate with dividing walls  134  when the first legs are in an unmated condition. It is important to note that first leg receiving cavities  136  are dimensioned to receive first legs  154  thereby allowing the first legs to move from an unmated or slightly prestressed position to a mated position.  
         [0038]    Second legs  156  are positioned in second leg receiving cavities  138 . Unlike the first legs, second legs  156  do not extend beyond mating surface  120 . Free ends  166  of the second legs are provided at an angle relative to the second legs. This allows free ends  166  to engage dividing walls  134 . Lead-in surfaces  168  are provided at free ends  166  of second legs  156 .  
         [0039]    Referring to FIG. 7, bus bar ground plane mating terminals  170  are positioned in second connector housing  18 . Bus bar ground plane mating terminals  170  have connector mating portions  172  and circuit board mating pins  174 . Connector mating portions  172  have an essentially U-shaped configuration, with enlarged contact projections  176  provided at the free ends thereof. Circuit board mating pins  174  have enlarged securing projections  178  which cooperate with the side walls of receiving recess  148  to maintain the bus bar ground plane mating terminals  170  in the recess.  
         [0040]    First printed circuit board  12  (FIGS.  1 - 4 ) has conductive signal paths  210  provided on the opposing top and bottom surfaces  212 . Conductive grounding planes  214  are positioned below opposing top and bottom surfaces  212  (FIG. 3). The conductive grounding planes  214  include conductive edge surfaces  220  that are exposed at the peripheral edge surfaces extending between opposing top and bottom surfaces  212 .  
         [0041]    Second printed circuit board  14  (FIGS. 1 and 7), has conductive signal paths  230  provided on at least one top or bottom surface  232 . Conductive grounding planes (not shown) are positioned below top or bottom surface  232 . The conductive grounding planes include conductive edge surfaces  220  that are exposed at the peripheral edge surfaces extending between opposing top and bottom surfaces  232 .  
         [0042]    In operation, first connector housing  16  is positioned in electrical engagement with first printed circuit board  12 . In order to accomplish this electrical connection, a fully assembled first connector housing  16 , with bus bars  70  provided therein, is positioned in some type of mounting fixture (not shown). The mounting fixture can be a standard type mounting fixture which is dimensioned to receive first connector housing  16 . It is important that the mounting fixture be dimensioned to support bus bars  70  in the housing, as bus bars  70  are only positioned in the housing with an interference fit. First connector housing is positioned in the fixture such that mating legs  58  and circuit board mating pins  74  extend outward.  
         [0043]    With first connector housing  16  properly positioned in the fixture, the first connector housing is aligned in coplanar confronting relation with first printed circuit board  12 , and then moved into engagement with first printed circuit board  12 . In particular, the first connector housing is moved into engagement with the edge surface  220  of printed circuit board  12 . As first connector housing  16  and first circuit board  12  are moved into engagement, printed circuit board mating legs  58  engage edge surface  220  of first circuit board  12 . It should be noted that the distance provided between the free ends of opposed mating legs  58  is less than the width of the first printed circuit board  12 . Consequently, when the printed circuit board mating legs  58  first engage first printed circuit board  12 , legs will contact edge surface  220 . Upon further insertion of first connector housing  16  onto first printed circuit board  12 , legs  58  are force to spread apart and slide over opposing top and bottom surfaces  212 . This motion continues until first connector housing  16  is fully inserted onto printed circuit board  12 , thereby positioning legs  58  in electrical engagement with conductive signal paths  210 . The electrical engagement between legs  58  and conductive signal paths  210  is ensured due since legs  58  are provided in a prestressed position, and consequently provide a significant normal force on the conductive signal paths.  
         [0044]    As first connector housing  16  mates with printed circuit board  12 , biasable structures  74  also cooperate with first circuit board  12 . More particularly, biasable structures  74  engage edge surface  220  of printed circuit board  12  after mating legs  58  have begun sliding over opposing top and bottom surfaces  212 . It is important to note that biasable structures  74  must be provided in alignment with the conductive portions of edge surface  220  as the mating occurs. Biasable structures  74  must exert a force on conductive side edge surface  220  to electrically and mechanically engage conductive edge surface of the printed circuit board&#39;s ground plane without projecting into or extending through that edge surface in anyway. For example, cantilever springs may be employed as biasable structures  74 . In this case, biasable structures  74  would be formed integrally with the edge of bus bar ground plane  70 . Alternatively, biasable structures  74  may be a combination of compression spring and contact is arranged on bus bar ground plane  70  so as to project outwardly from a free edge. Advantageously, biasable structures  74  resiliently cooperate with conductive edge surface  220  of printed circuit board  12  to provide electrical and mechanical engagement between bus bar ground plane  70  and a ground plane positioned within printed circuit board  12 , without projecting into or extending through edge surface  220  of printed circuit board  12 .  
         [0045]    With first connector housing  16  fully inserted on first circuit board  12 , printed circuit board mating legs  58  are soldered to conductive signal paths  210 . This solder connection also acts to maintain printed circuit board  12  in close engagement with first connector housing  16  in opposition to the force applied to conductive edge surface  220  by biasable structure  74 . This provides the mechanical and electrical connections required between first connector housing  16  and first printed circuit board  12 .  
         [0046]    The are several advantages of utilizing a connector which is mounted onto the side surface of a circuit board. First, as the sophistication of equipment increases, more connectors are required to be positioned on circuit boards. As there is a limited amount of space available, solutions must be found to increase the amount of connectors mated to the circuit board. This invention allows the edges or side surfaces of the circuit board to be utilized for the mating of connectors. Also, the placement of the connectors on the side surfaces of the circuit board allows for relatively short path lengths across which the signals travel, thereby minimizing the propagation delay associated with the connector.  
         [0047]    With the insertion of the first connector housing  16  onto the first circuit board complete, the fixture can be removed from the housing.  
         [0048]    Second connector housing  18  is positioned on second circuit board  14  (FIGS.  1 - 5 ). During this process, circuit board mating pins  174  are inserted into openings  238  provided on printed circuit board  14 . As pins  174  are inserted into openings  238 , printed circuit board mating legs  158  engage conductive signal paths  230  provided on surface  232  of printed circuit board  230 . The engagement of legs  158  with paths  230  defines the fully inserted position of second connector housing relative to second circuit board. With the second connector housing fully inserted, pins  174  are soldered in openings  238  and legs  158  are soldered to conductive paths  230 . This provides the mechanical and electrical connection required between second connector housing  18  and second circuit board  14 . Circuit board mating legs  58 , 158  have arcuate surfaces provided at their ends. The solder cooperates with the arcuate surface to provide the mechanical and electrical interconnection with the circuit boards. The configuration of the arcuate surfaces helps to insure that the solder will not crack. In other words, the use of mating legs which have flat surfaces promotes the solder to crack, thereby causing an unreliable connection.  
         [0049]    With the first and second connector housings  16 , 18  properly mounted to the circuit boards  12 , 14 , the connector housings are mated together.  
         [0050]    The first connector housing  16  is positioned proximate the second connector housing  18  such that the mating connector receiving recess  30  of the first housing is in alignment with the second connector housing. Mating connector receiving recess  30  is dimensioned to allow second connector housing  18  to be inserted. To mate the connector housings together, the first connector housing  16  is moved from an initial position (FIG. 5) to a final or assembled position (FIG. 6). As the connector housings are moved to the assemble position, first connector terminals  50  engage second connector terminals  150  to provide the electrical connection required.  
         [0051]    As the mating occurs, the enlarged contact sections  62  of first legs  54  of first connector terminals  50  engage lead-in surfaces  168  of second legs  156  of second connector terminals  150 . At the same time, enlarged contact sections  162  of first legs  154  of second connector terminals  150  engage lead-in surfaces  68  of second legs  56  of first connector terminals  50 . Enlarged contact sections  62 ,  162  are then slide over lead-in surfaces  168 , 68 , thereby positioning enlarged contact sections  62 , 162  on side surfaces of second legs  156 ,  56 . Several functions are performed by the lead-in surfaces. The lead-in surfaces compensate for any slight misalignment of the terminals when mating occurs. The lead-in surfaces also cause first legs  54 , 154  to be moved to a stressed position, such that enlarged contact sections  62 ,  162  will provide a significant normal force on second legs  156 ,  56  when the contact sections are slid over the second legs.  
         [0052]    As the mating of the connectors continues, enlarged contact sections  62 , 162  will be slid on the side surfaces of second legs  156 ,  56  to fully assembled position (FIG.  6 ). This sliding engagement of the enlarged contact sections provides a wiping action under significant normal force conditions, thereby helping to ensure for a positive electrical connection between enlarged contact sections  62 , 162  and second legs  156 ,  56 . It should be noted that as enlarged contact sections  62 ,  162  of first legs  54 ,  154  are slid over second legs  156 ,  56 , walls of the housings prevent first legs  54 ,  154  from taking a permanent set. In other words, the walls of the housings are provided in close proximity to first legs  54 ,  154 , thereby insuring that the first legs can not be deformed beyond their elastic limit. This type of terminal configuration allows for a connector which requires a minimal height for operation. As the entire length of first legs  54 ,  154  are used for a resilient beam, the overall height of the connector can be minimized. In other words, the stationary portions of the terminals are provided on the second legs of the terminals, which is physically distinct from the first legs. Consequently, as no stationary portions are required on the first legs, the overall height of the first legs is minimized. It is also important to note that second legs  56 ,  156  are used only as stationary members, i.e. no resilient characteristics are required. Consequently, the second legs can be secured in the housings and be used to stabilize the terminals in the housings.  
         [0053]    The configuration of the terminals also provides for a reliable electrical connection. Each terminal provides two parallel paths over which the signal can travel. This provides for a redundant electrical connection, and results in a self inductance which is approximately half of that of a terminal with a single path. This is particularly advantageous in high speed applications.  
         [0054]    As the connector housings are mated together, bus bars  70  are positioned the bus bar mating terminals  170  (FIG. 7). The spacing between enlarged contact projections  176  of bus bar mating terminals  170  is less than the width of bus bars  70 . Consequently, the positioning of bus bars  70  in bus bar mating terminals  170  causes the contact projections to be spread apart, which in turn causes contact projections  176  to exert the normal force required on bus bars  70 .  
         [0055]    With the connector housing mated together effective electrical connection is provided between first circuit board  12  and second circuit board  14 . The connection is provided utilizing minimal space, as the first connector housing is mated to the edge and top and bottom surfaces of first circuit board. This is of great benefit, particularly as board real estate is at a premium.  
         [0056]    Although the connector assembly described provides an electrical connection between two printed circuit boards, the principal of the invention can be utilized in other types of connector assemblies, i.e a cable to board connector assembly.  
         [0057]    It is to be understood that the present invention is by no means limited only to the particular constructions herein disclosed and shown in the drawings, but also comprises any modifications or equivalents within the scope of the claims.