Abstract:
An electrical connector, comprising: a frame; a housing; and a cover. A contact extends through the housing, which secures to the frame. The cover secures to the frame and moves relative to the housing between a first position and a second position. An electrical connector may connect an electrical component having a terminal to a substrate having a conductive element. The housing has: a contact mounted to the substrate and adapted to engage a terminal of the electrical component, and guidance structure. The frame mounts to the substrate and supports the housing. An insert mounts to an opening in the cover and includes guidance structure corresponding to the guidance structure on the housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 60/147,118, filed on Aug. 4, 1999, and No. 60/147,120, filed on Aug. 4, 1999, both of which herein incorporated by reference. 
    
    
     BACKGROUND OF INVENTION 
     1. Field of the Invention 
     The present invention relates to electrical connectors. More specifically, the present invention relates to zero insertion force (ZIF) sockets. 
     2. Brief Description of Earlier Developments 
     A common application for ZIF sockets involves connecting a microprocessor to a circuit board. Each subsequent microprocessor generation poses greater demands on the socket design. For example, new microprocessor may require smaller centerline spacing between contacts, greater pin count, increased coplanarity or decreased mating height. While conventional socket designs provide suitable results for existing microprocessors, these socket designs may not prove adequate in future generations of microprocessors. 
     SUMMARY OF INVENTION 
     It is an object of the present invention to provide an electrical connector that exhibits reduced stress levels at the solder joints. 
     It is a further object of the present invention to provide an electrical connector capable of accommodating mismatches in the coefficients of thermal expansion (CTE) of the various material used in the electronic device. 
     It is a further object of the present invention to provide a socket that does not transmit forces caused by actuation of the socket to the solder joints. 
     It is a further object of the present invention to provide an electrical connector having satisfactory coplanarity. 
     It is a further object of the present invention to provide an electrical connector with improved manufacturability. 
     It is a further object of the present invention to provide an electrical connector exhibiting improved mold flow characteristics. 
     It is a further object of the present invention to provide an electrical connector with improved reliability. 
     It is a further object of the present invention to provide an electrical connector that exhibits greater flexibility. 
     It is a further object of the present invention to provide an electrical connector with a contact housing having greater compliancy. 
     It is a further object of the present invention to provide an electrical connector modularly assembled from several components. 
     It is a further object of the present invention to provide an electrical connector formed from loosely coupled components. 
     It is a further object of the present invention to provide an electrical connector having a reduced mating height. 
     These and other objects of the present invention are achieved in one aspect of the present invention by an electrical connector, comprising: a frame; a housing having a contact extending therethrough and secured to the frame; and a cover secured to the frame and movable relative to the housing between a first position and a second position. 
     These and other objects of the present invention are achieved in another aspect of the present invention by a socket for connecting an electrical component to a substrate, comprising: a housing; a frame mountable to the substrate and supporting the housing; a cover movably secured to the frame between a first and a second position; and an insert mountable to said opening in said cover. The housing includes: a contact mountable to the substrate and adapted to engage a terminal of the electrical component; and guidance structure. The cover includes an opening. The insert includes guidance structure corresponding to the guidance structure on the housing so that the insert aligns with the housing. 
     These and other objects of the present invention are achieved in another aspect of the present invention by an electrical system, comprising: an electrical component having a terminal; a substrate having a conductive element; and an electrical connector mounted to the substrate and adapted to removably secure the electrical component to the substrate. The connector comprises housing; a frame mountable to the substrate and supporting the housing; and a cover movably secured to the frame between a first and a second position. The housing includes: a contact mounted to the substrate and adapted to engage a terminal of the electrical component, and guidance structure. The cover includes an opening. The insert mounts to the opening in the cover and includes guidance structure corresponding to the guidance structure on the housing so that the insert aligns with the housing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other uses and advantages of the present invention will become apparent to those skilled in the art upon reference to the specification and the drawings, in which: 
     FIG. 1 a  is a top perspective view of an electrical connector of the present invention; 
     FIG. 1 b  is a bottom perspective view of the electrical connector in FIG. 1 a;    
     FIG. 2 is an exploded view showing the various components of the electrical connector in FIG. 1 a;    
     FIG. 3 a  is a top perspective view of one sub-assembly of the electrical connector in FIG. 1 a;    
     FIG. 3 b  is a bottom perspective view of the sub-assembly in FIG. 3 a;    
     FIG. 4 a  is a top perspective view of one component of the electrical connector in FIG. 1 a;    
     FIG. 4 b  is a bottom perspective view of the component in FIG. 4 a;    
     FIG. 4 c  is a detailed plan view of the component in FIG. 4 a;    
     FIG. 4 d  is a cross-sectional view of the component in FIG. 4 c  taken along line  4   d — 4   d;    
     FIG. 5 a  is a top perspective view of another component of the electrical connector in FIG. 1 a;    
     FIG. 5 b  is another top perspective view of the component in FIG. 5 a;    
     FIG. 5 c  is a top perspective view of the component in FIG. 5 a  partially assembled; 
     FIG. 6 a  is a top perspective view of another sub-assembly of the electrical connector in FIG. 1 a;    
     FIG. 6 b  is a bottom perspective view of the sub-assembly in FIG. 6 a;    
     FIG. 7 a  is a top perspective view of another component of the electrical connector in FIG. 1 a;  and 
     FIG. 7 b  is a bottom perspective view of the component in FIG. 4 a.   
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1 a  and  1   b  provide a top and a bottom perspective view, respectively, of an assembled electrical connector of the present invention. Generally speaking, the present invention is a socket  100  used to connect a first electrical component to a second electrical component. More specifically, socket  100  connects a microprocessor interposer I having pins P disposed in an array (e.g. PGA) to a motherboard M. Socket  100  preferably receives interposer pins P with zero insertion force. 
     Although the figures display socket  100  surface mounted to motherboard M, other mounting methods could be used. If, however, socket  100  is surface mounted as shown in the figures, ball grid array (BGA) technology is preferred. 
     Socket  100  is modular, made from several interengageable components. The components are designed to be flexible. When compared to a comparable unitary structure, the modular socket of the present invention is less rigid. Accordingly, the present invention can better handle stress build up caused by CTE differential between the various materials used in the interposer I, motherboard M and the socket. The present invention can also better handle stresses caused by the mating of the interposer pins P and the socket contacts than a comparable unitary structure. 
     A top  101  of socket  100  faces, and receives, interposer I. A bottom  103  of socket  100  faces, and mounts to, motherboard M. Although the various figures demonstrate socket  100  as being actuated by a hand tool T, such as a screwdriver, other actuation mechanisms (e.g. a lever rotating an eccentric cam) could be used. 
     As seen in FIG. 2, numerous components form socket  100 . Socket  100  could include, for example, a cover  203 , an insert  205 , contacts  303 , contact housing  305 , solder masses  307  and base frame  401 . Cover  203  and insert  205 , when assembled together, form cover sub-assembly  201 . Contacts  303 , housing  305  and solder masses  307 , when assembled together, form contact housing sub-assembly  301 . As described in more detail below, assembly of socket  100  involves placing contact housing sub-assembly  301  into base frame  401 , then securing cover sub-assembly  201  over base frame  401 . 
     Rather than rigidly assembling all of the sub-assemblies together, the present invention loosely couples the sub-assemblies. In other words, the sub-assemblies are not interference fit together. Rather, the various surfaces of the sub-assemblies abut without interference. 
     Without interference fitting, the present invention encourages some movement between the sub-assemblies. The relative movement of the sub-assemblies as a result of the aforementioned loose coupling helps absorb the stress caused by CTE differential and by the mating of interposer pin P and contacts  303 . Whereas a rigid socket would transmit the stresses to the solder joint, a loosely coupled connector does not transmit all of the forces between connected components. Rather, the loosely coupled components individually absorb any stresses. Any stress that might be transmitted between adjacent components is generally an insignificant amount. 
     The movement between loosely coupled components, while large enough to prevent stress build up in the solder joints, should also be sufficiently small to ensure and maintain proper orientation between the respective sub-assemblies. 
     FIGS. 3 a  and  3   b  display cover  203 , which is preferably stamped and formed from a suitable metal. Although metal is preferred in situation where a short mating height is required, other materials, including insulative materials, could be used. 
     Bending cover  203  along both sides creates an upper wall  207  and sidewalls  209 . Since cover  203  must move across base frame  401 , the longitudinal axes of sidewalls  209  define the actuation direction indicated by line A. 
     Upper wall  207  has a central opening  211  that receives insert  205 . Preferably, insert  205  is molded around opening  211 . However, other methods of making insert  205  are possible. For example, insert  205  could be molded separately from cover  203 , then latched into cover  203  in a fashion similar to the latching arrangement of contact housing sub-assembly  301  and base frame  401  discussed in more detail below. 
     Upper wall  207  also has depressed regions  213 . Depressed regions  213  include an aperture  215  and help retain cover  203  on base frame  401 . As shown in FIGS. 3 a  and  3   b,  aperture  215  preferably has a T-shape, with enlarged portions  231  and a smaller portion  233 . 
     Opposed edges of upper wall  207  include notches  217 . Notches  217 , conjunction with openings in base frame  401 , allow tool T to actuate socket  100  between an open and a closed position. 
     FIGS. 3 a  and  3   b  display insert  205 . Preferably, insert is made from a suitable insulative material such as a high temperature thermoplastic like a liquid crystal polymer (LCP). Insert  205  has a base  219  with plurality of apertures  221  extending therethrough. Apertures  221  are large enough to allow interposer pins P to pass freely therethrough without interference, but are small enough to provide lateral support to interposer pin P during mating with contacts  303 . 
     The pattern of apertures  221  on cover  201  corresponds to the pattern of interposer pins P. The present invention could, however, have patterns arranged differently than that shown in FIG. 3 a  in order to receive other interposers (such as an interposer with an interstitial pin grid array). 
     If designed for one specific interposer, the number of apertures  221  preferably equals the number of interposer pins P. In order to, for example, accommodate interposers with differing pin counts, socket  100  could have more apertures  221  than interposer pins P. 
     Insert  205  also includes keyways  223  aligned with the actuation direction designated by arrow A. Keyways  223  receive splines  341  (as shown in FIG. 4 a ) from contact housing  305 . A guide surface  225  extends in the actuation direction. Opposed stop surfaces  226 ,  227  flank guide surface  225 . 
     Guide surface  225  abuts, without interference, a corresponding guide surface  343  (as shown in FIG. 4 a ) on the splines of contact housing  305 . This interaction ensures proper alignment of contact housing  305  (and, necessarily, contacts  303 ) with insert  205  (and, necessarily, interposer pins P). 
     Stop surfaces  226 ,  227  abut corresponding stop surfaces  345 ,  347  (as shown in FIG. 4 a ) on the splines of contact housing  305 . In the open position, stop surface  226  abuts the corresponding stop surface. In the closed position, stop surface  227  abuts the corresponding stop surface. In other words, the stop surfaces determine the travel of cover sub-assembly  201  across base frame  401  and define the open and closed positions. 
     FIGS. 4 a - 4   d  display contact housing  305 . Preferably made from a suitable insulative material such as a high temperature thermoplastic, housing  305  includes a base  309  and a peripheral wall  311 . Base  309  includes an array of apertures  333  which accept contacts  303 . Apertures  333  have tapered sidewalls to limit the insertion of contact  303 . The end of aperture  333  adjacent motherboard M could have an enlarged recess  349 . Recess  349  would allow a portion of solder mass  307  to reside therein when secured to contact  303 . 
     A pair of the opposed sidewalls that form aperture  333  can each include a deformable rib  335 . Preferably, the deformable ribs  335  are centrally located along the sidewalls. Deformable rib  335  engages contact  303  upon insertion into aperture  333 . 
     Peripheral wall  311  includes features that help retain contact housing  305  within base frame  401 . Opposed sides of wall  311  include latch structure  337 . Latch structure  337  engages a corresponding latch on base frame  401 . Latch structure  337  includes a tapered surface  351  and a bottom surface  353 . 
     Other opposed sides of wall  311  include keys  339 . Keys  339  reside within corresponding notches in base frame  401  without interference. Keys  339 , in conjunction with notches, help align contact housing sub-assembly  301  and base frame  401 . Each key  339 , and the corresponding notch, could have a different size in order to allow contact housing sub-assembly  301  to engage base frame  401  in only one orientation. 
     Peripheral wall  311  also includes features that align contact housing sub-assembly  301  and cover assembly  201 . Opposed sides of wall  311  have splines  341  extending upwardly therefrom. Splines  341  extend past the upper surface of wall  311  in order to reside within keyways  223 . 
     Splines  341  include a guide surface  343  flanked by opposed stop surfaces  345 ,  347 . As discussed earlier, guide surface  343  abuts guide surface  225  of insert  205 , without interference, to align contact housing sub-assembly  301  and cover assembly  201  also, stop surfaces  345 ,  347  abut corresponding stop surfaces  227 ,  229  on insert  205  to define the open and closed positions of socket  100 . 
     FIGS. 5 a - 5   c  display contact  303 . As seen in FIG. 5 c,  contact  303  is preferably stamped and formed from a carrier strip  313  made from a suitable conductive material such as a copper alloy. 
     Contact  303  has dual beams  315 , 317  extending from one end of a base section  319 . Each beam  315 ,  317  has a respective lead-in portion  321 , 323  between which interposer pin P enters when socket  100  receives interposer I. Actuation of socket  100  towards a closed position moves interposer pin P towards respective mating portions  325 , 327  of beams  315 ,  317 . Mating portions  325 ,  327  engage opposite sides of interposer pin P. 
     As seen in FIG. 5 a,  beam  315  is shorter than beam  317 . Although engaging opposite sides of interposer pin P, beams  315 , 317  engage pin P at a different elevations. In order to balance the spring rates of beams  315 ,  317 , the width of long beam  317  can be greater than the width of short beam  315 . 
     A mounting section  329  extends from an opposite end of base section  319  and is flanked by a pair of shoulders  331 . Preferably, mounting section  329  is a surface mount section. Although any surface mount termination could be used, FIGS. 5 a  and  5   b  show the preferred contact  303  capable of surface mounting to motherboard M using BGA technology. Furthermore, other mounting techniques (e.g. pin-in-paste, press-fit) could be used. International Publication numbers WO 98/15989 and WO 98/15991, herein incorporated by reference, describe methods of securing a solder mass  307 , such as a fusible solder ball, to a contact retained by an insulative housing and to a pad on a circuit substrate. 
     The assembly of contact housing sub-assembly  301  will now be described. First, contacts  303  are inserted into apertures  333  in housing  305 . Insertion is complete when shoulders  331  abut a correspondingly shaped feature in aperture  333 . In that position, beams  315 , 317  extend upwardly from housing  305  and mounting portion  329  extends downwardly from housing  305 . 
     Next, solder mass  307  is secured to contact  303  using, for example, the reflow techniques described in International Publication numbers WO 98/15989 and WO 98/15991. The combination of shoulder  331  of contact  303  abutting the surface of aperture  333  and of solder mass  307  securing to mounting end  329  of contact  303  serves to hold contact housing sub-assembly  301  together. FIGS. 6 a  and  6   b  display an assembled contact housing sub-assembly  301 . 
     FIGS. 7 a  and  7   b  display base frame  401 . Base frame  401 , formed from a suitable insulative material such as a high temperature thermoplastic, has a generally rectangular shape. Base frame  401  has a central opening  403  in which contact housing sub-assembly  301  resides upon assembling socket  100 . 
     Sidewalls  405  that define central opening  403  include features that help retain contact housing sub-assembly  301  in base frame  401 . Sidewalls  405  include pockets  409 . A bottom surface  411  helps define pocket  409 . Pockets  409  reduce the thickness of sidewall  405  so that, in these areas, sidewall  405  acts like a latch. 
     During initial insertion of contact housing sub-assembly  301  into base frame  401 , tapered surface  351  of contact housing  305  engages bottom surface  411  of sidewall  405 . Accordingly, sidewall  405  deflects upon further insertion of contact housing sub-assembly  301 . Once tapered surface  351  passes bottom surface  411 , sidewall  405  resiles to its original position. At this position, bottom surface  411  of sidewall  405  abuts bottom surface  353  of contact housing  305  without interference. This prevents contact housing sub-assembly from exiting base frame  401  in one direction. 
     Sidewalls  405  also have elongated slots  407 . Slots  407  receive splines  341  without interference. Slots  407  help align contact housing sub-assembly  301  within base frame  401 . 
     Base frame  401  also includes channels  413  on a lower surface. Channels  413  receive blocks  339  of contact housing  305 . Channels  413  prevent contact housing sub-assembly  301  from exiting base frame  401  in  15  one direction. Channels  413 , in conjunction with the latch feature of sidewalls  405 , serve to prevent contact housing sub-assembly  301  from exiting base frame  401  after insertion. Channels  413  and the latch features do not, however, interference fit contact housing sub-assembly  301  and bases frame  401  together. 
     Base frame  401  includes posts  415  extending upwardly therefrom. Posts  415  retain cover sub-assembly  201  on base frame  401 . Posts  415  include a body portion  417  and an enlarged head  419 . In order to secure cover sub-assembly  201  to base frame  401 , enlarged heads  419  are extended through enlarged portions  231  of apertures  215 . Then, cover sub-assembly is slid along base frame  401  until enlarged heads  419  are positioned over smaller portions  233  of apertures  215 . 
     At this point of assembly, cover sub-assembly  201  cannot be removed unless cover  203  is slid so that enlarged heads  419  and enlarged portions  231  of aperture  215  align. However, once contact housing sub-assembly  301  is inserted into base frame  401 , enlarged heads  419  and enlarged portions  231  of aperture  215  cannot align. 
     Base frame  401  includes an opening  421  which can receive tool T. Opening  421  acts as a leverage point to drive cover sub-assembly  201  across base frame  401  between the open and closed positions. 
     The bottom surface of base frame  401  also includes solder pads  423  for surface mounting to motherboard M. As discussed earlier, if a technique other than surface mounting is used, solder pads  423  may not be required. 
     The assembly of socket  100  will now be described. First, the sub-assemblies are built as discussed above. Second, cover sub-assembly  201  is secured to base frame  401  by engaging posts  415  with openings  215 . Finally, contact housing sub-assembly  301  is inserted into central opening  403  of base frame  401 . During insertion, splines  341  of contact housing sub-assembly  301  enter keyways  223  of cover sub-assembly  201 . 
     Once fully assembled, socket  100  can receive interposer I. Interposer pins P enter apertures  221  in insert  205 . Socket  100  can now be actuated from an open to a closed position. In the closed position, contacts  303  engage interposer pins. 
     Due to the loose coupling of the components of socket  100 , the components generally absorb most of the stresses caused by CTE differential and the mating process. The components typically prevent stress build-up in the solder joints. 
     While the present invention has been described in connection with the preferred embodiments of the various figures, it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiment for performing the same function of the present invention without deviating therefrom. Therefore, the present invention should not be limited to any single embodiment, but rather construed in breadth and scope in accordance with the recitation of the appended claims.