Abstract:
A zero insertion force socket is provided having a cover and housing sidably mounted to one another. The housing includes a pocket receiving a cam assembly. The cam assembly is slidably moveable within the housing in a direction perpendicular to the direction of movement between the cover and housing. The lever is rotatably mounted within the housing and engages the cam assembly to transfer rotational movement of the lever into axial movement of the cam assembly in a transverse direction. The cam assembly communicates with the cover such that the cam assembly drives the cover in a longitudinal direction as the cam assembly moves in a transverse direction. The lever and cam assembly cooperate to spread actuation forces across the cover and housing.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 09/672,561 filed Sep. 28, 2000, now U.S. Pat. No. 6,338,639, which claims priority from Provisional Application No. 60/202,987 filed May 9, 2000, and these prior applications are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The preferred embodiments of the present invention generally relate to electrical sockets, such as pin grid array (PGA) sockets. More specifically, the preferred embodiments of the present invention generally relate to zero insertion force (ZIF) processor sockets. 
     Heretofore, PGA sockets have been proposed that include a base having a cover slidably mounted thereon. The sliding motion between the base and cover is controlled in numerous manners in conventional ZIF PGA sockets. For example, U.S. Pat. No. 5,256,080 discloses a bail actuated ZIF socket. U.S. Pat. No. 5,730,615 describes a ZIF PGA socket that uses a flat or plate tool that is inserted into receiving slots in the cover and base. The flat tool is moved between two positions in order to open and close the ZIF socket. U.S. Pat. No. 4,498,725 discloses a prior art PGA socket having a base housing and a moveable cover. An L-shaped lever moves the cover across a top surface of the housing. The lever includes a first arm that is rotatably received in a passage in the socket and a second arm that provides a handle for rotating the first arm. 
     However, existing ZIF sockets have experienced limited applicability to certain processor designs. For instance, many circuit designs are conditioned on PGA chips being arranged in a closely packed manner with respect to one another. For instance, at least one conventional socket uses an actuation lever located along one side of the socket and is moved in the same direction as the direction of relative movement between the cover and base housing. For instance, the lever is moved forward along the side of the socket to drive the cover forward and visa versa. However, as components decrease in size and are located closer to one another, space constraints no longer permitted the lever to be located along the side of the socket. Thus, it is desirable to minimize the width of sockets holding the PGA chips. 
     Also, as chip technology evolves, the number of pins on a single chip increases. The socket achieves a separate electrical contact with each pin on a chip and thus the number of electrical contacts to be maintained by a socket is increased. As the pin/contact count increases, the force required to electrically engage the chip and socket similarly increases. Conventional sockets focus significant actuation forces on small areas on the cover and housing. As the actuation forces increase, various socket designs experience more faults as the housing and cover are unable to withstand the increased loads. Conventional sockets for high pin count PGA chips do not spread actuation forces over the entire housing/cover. 
     A need remains for an improved socket. It is an object of the preferred embodiments of the present invention to meet this and other needs that will become apparent from the following description, drawings and claims. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with at least one preferred embodiment, a socket is provided for an electronic package. The socket includes a cover and base housing that are slidably engaged with one another. The cover and base housing are moveable between open and closed positions along a socket longitudinal axis. The socket further includes an actuation member configured to move the cover when the actuation member is rotated about a rotational axis. The actuation member is aligned such that the rotational axis of the actuation member is parallel to the socket longitudinal axis along which the cover and base housing move relative to one another. The actuation member drives the cover along the longitudinal axis between open and closed positions when the actuation member is rotated about the rotational axis. 
     In accordance with at least one alternative embodiment, the actuation member comprises a cam assembly slidably received within a journaled portion of the base housing. The cam assembly transfers rotary motion of the actuation member about the rotational axis to linear motion along the longitudinal axis. In accordance with at least one alternative embodiment, the cam assembly has at least one pusher bar mounted thereon. The pusher bar slidably engages the cover to drive the cover between open and closed positions. The cam assembly may include a plurality of pusher bars and the cover may include an equal plurality of slots slidably receiving the pusher bars. The pusher bars and slots are aligned at an angle to the socket longitudinal axis such that movement of the actuation member along a transverse axis in a direction at an angle to the socket longitudinal axis drives the cover along the longitudinal axis. The chamber in the base housing or cover may be located near the rear end thereof. The chamber includes tracks along opposite sides that receive a cam assembly included within the actuation member. The cam assembly is movable within the tracks laterally from one side to the other side of the base housing or cover. 
     In accordance with at least one alternative embodiment, the actuation member includes a lever having a handle and a leg. The leg includes an offset cam journal movable along an arcuate path when the handle is rotated about the rotational axis. The cam journal causes the cover to open and close when the handle is rotated. The actuation member may include a main journaled portion extending along a common axis that defines the rotational axis and that is separated by an offset cam journal. The chamber in one of the base housing and cover may include cutouts that receive the main journaled portions. The cutouts may be positioned to align the rotational axis parallel to the longitudinal axis. 
     In accordance with at least one alternative embodiment, the actuation member includes a rotating lever and a sliding cam. The rotating lever is rotatable about a rotational axis to drive the sliding cam in a direction perpendicular to the longitudinal axis. The sliding cam drives the cover along the longitudinal axis. The actuation member engages the cover at multiple points evenly distributed along a width of the cover between the sides of the cover thereby spreading actuation force over a wide surface area of the cover. 
     In accordance with yet a further alternative embodiment, the actuation member includes a handle and a leg rotatable about the rotational axis. The leg includes threads engaging corresponding threads in at least one of the cover and base housing. The leg drives the cover between open and closed positions as the handle is rotated. The actuation member may include one or more threaded shafts located near the rear end of the base housing and evenly distributed between sides of the base housing. The threaded shaft causes the cover to move when the shaft is rotated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing summary, as well as the following detailed description of the preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings embodiments which are present preferred. It should be understood, however, that the present invention is not limited to the precise arrangements and instrumentality shown in the attached drawings. 
     FIG. 1 illustrates a perspective view of a socket in accordance with a preferred embodiment of the present invention while in an open position. 
     FIG. 2 illustrates an end view of a socket in accordance with a preferred embodiment of the present invention while in an open position. 
     FIG. 3 illustrates a perspective view of a socket in accordance with a preferred embodiment of the present invention while in a closed position. 
     FIG. 4 illustrates an end view of a socket in accordance with a preferred embodiment of the present invention while in a closed position. 
     FIG. 5 illustrates an exploded perspective view of a socket in accordance with a preferred embodiment of the present invention. 
     FIG. 6 illustrates a detailed view of a portion of the underside of the cover of a socket in accordance with a preferred embodiment of the present invention. 
     FIG. 7 illustrates a perspective view of the base housing of a socket in accordance with a preferred embodiment of the present invention. 
     FIG. 8 illustrates a perspective view of the underside of the cover of a socket in accordance with a preferred embodiment of the present invention. 
     FIG. 9 illustrates a cam assembly slidably received within the base housing of a socket in accordance with a preferred embodiment of the present invention. 
     FIG. 10 illustrates the underside of a cam assembly utilized in accordance with a preferred embodiment of the present invention. 
     FIG. 11 illustrates a wear plate to be securely mounted to a cam assembly in accordance with a preferred embodiment of the present invention. 
     FIG. 12 illustrates an actuation lever rotatably housed between the cover and the base housing of a socket in accordance with a preferred embodiment of the present invention. 
     FIG. 13 illustrates a perspective view of a socket in accordance with an alternative embodiment of the present invention. 
     FIG. 14 illustrates a cross-sectional view taken along line  14 — 14  in FIG. 13 of a socket in accordance with an alternative embodiment of the present invention. 
     FIG. 15 illustrates a perspective view of a cam assembly constructed in accordance with an alternative embodiment of the present invention. 
     FIG. 16 illustrates a top view of a portion of the base housing as constructed in accordance with an alternative embodiment of the present invention. 
     FIG. 17 illustrates a top perspective view of a portion of the inside of the cover as constructed in accordance with an alternative embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1-2 and  3 - 4  illustrate a socket  10  in accordance with a preferred embodiment of the present invention when in opened and closed positions, respectively. The socket  10  includes a front  11 , back end  13 , and sides  15  and  17 . The socket  10  generally includes a base housing  12  and a cover  14  slidably engaging one another. The base housing  12  and cover  14  are moved between open and closed positions (FIGS. 1 and 3, respectively) by moving a lever  16  between an open position (FIG. 2) and a closed position (FIG.  4 ). The cover  14  includes a processor pin pattern  18 . The base housing  12  includes a pin pattern  20  (FIG. 7) associated with the pin pattern  18 . 
     FIG. 5 illustrates an exploded view of the socket  10 . The base housing  12  includes a rectangular journaled portion  22  that receives a rectangular cam assembly  24 . The cam assembly  24  is slidably movable within the journaled portion  22  in a lateral direction (from side to side) denoted by arrow A. A metal wear plate  26  is securely mounted to an under surface of the cam assembly  24 . The wear plate  26  rotatably communicates with an actuation lever  28 . The journaled portion  22  includes tracks  23  (FIG. 7) along opposite sides thereof to permit lateral movement of the cam assembly  24 . The actuation lever  28  includes a handle  30  and a leg  32 . The leg  32  includes main journal portions  34  and  36  extending along a common longitudinal axis and separated by an offset cam journal  38 . The main journaled portions  34  and  36  are received within cut-outs  40  and  42  in the base housing  12  located on either side of the journaled portion  22 . The cam journal  38  rotatably contacts the metal wear plate  26 . 
     Once assembled, when the handle  30  is moved along the arcuate path designated by arrow B in FIG. 2, the leg  32  rotates about its longitudinal axis, thereby causing the cam journal  38  to similarly pivot along an arcuate path. As the cam journal  38  pivots along an arcuate path, the interaction between the cam journal  38  and wear plate  26  drive the cam assembly  24  laterally along the direction designated by arrow A. 
     The cam assembly  24  includes a plurality of pusher bars  44  mounted on the upper surface  43  thereof. The pusher bars  44  are slidably received within slots  46  in the top  19  of the cover  14 . The pusher bars  44  are arranged such that the longitudinal axes of the pusher bars  44  extend parallel to one another and form an acute angle with respect to the longitudinal axis of the cam assembly  24 . By way of example only, the pusher bars  44  may extend at approximately a 25° angle with respect to the longitudinal axis of the cam assembly  24 . As the cam assembly  24  moves in the direction of arrow A, the pusher bars  44  slidably engage the sidewalls of the slots  46 , thereby causing the cover  14  to slide relative to the base housing  12  between the open and closed positions. By way of example, the cam journal  38  may be driven along an arcuate path E (FIG. 12) aligned in a vertical plane extending perpendicular to the longitudinal axis of the cam assembly  24 . The cam journal  38  drives the pusher bars  44  laterally with respect to the socket  10  causing the pusher bars  44  to move from one end to an opposite end of the slots  46  (as shown in FIGS.  1  and  3 ). As the pusher bars  44  move within slots  46 , the pusher bars  44  force the cover  14  to move in a direction C that is perpendicular to the lateral movement of the pusher bars  44 . The cover  14  moves between the front and back ends  11  and  13  of the socket  10 . 
     Optionally, the pusher bars  44  may be aligned at an angle to the longitudinal axis of the cam assembly  24  that is greater than or less than approximately 25°. The angular relation between the pusher bars  44  and the longitudinal axis of the cam assembly  24  may be adjusted based upon the amount of movement that is required between the cover  14  and the base housing  12 . Optionally, the number of pusher bars  44  may be increased or decreased, and the size of each pusher bar varied in order to further divide the actuating force along the width of the socket  10 . The cam assembly  24  and actuation lever  28  cooperate to spread the actuation force over a wide surface area of the socket  10 . In particular, the actuation force is divided along the adjoining surfaces of the slots  46  and pusher bars  44 . Thus, by varying the number and size of pusher bars  44  and slots  46 , the distribution of the actuation force may be similarly varied across the width of the cover  14 . The cam assembly  24  includes a central block section  48  to provide additional support and strength in the region at which the wear plate  26  and actuation lever  28  operate. 
     FIG. 7 illustrates a perspective view of the base housing  12  in more detail. The base housing  12  includes a front surface  55 , a back surface  57  and sides  59 . The cover  14  includes a front end wall  60 , side walls  84 , a bottom surface  82  and back edge  83 . The base housing  12  includes a pin pattern  20  associated with the pin pattern  18 . Optionally, the base housing  12  may include a plurality of core voids to prevent warping or distortion during manufacturing. The base housing  12  includes a plurality of latching surfaces  52  that slidably engage outer latches  54  on the cover  14  (FIG. 8) to retain the cover  14  in close proximity to the base housing  12 . The latches  54  and latching surfaces  52  cooperate to hold the cover  14  down upon the base housing  12 . A tab  56  on the base housing  12  is received within an opening  58  in the end wall  60  of the cover  14  to retain the base housing  12  and cover  14  in a desired relation to one another. A ledge  62  is formed along the front surface  55  of the base housing  12  to receive the end wall  60  when the socket  10  is closed. The journaled portion  22  includes an arcuate trough  64  centrally located therein traversing the journaled portion  22  to rotatably receive the leg  32  of the actuation lever  28 . Recessed notch portions  66 - 69  receive, and permit lateral movement of, the block section  48  of the cam assembly  24 . Pockets  70 - 73  snapably receive latches  74 - 77 , respectively, to securely retain the cover  14  against the base housing  12 , while permitting forward and reverse sliding movement between the base housing  12  and cover  14  in the direction designated by arrow C. A protective cover  80  is provided to receive the handle  30  of the actuation lever  28  while in a closed or locked position. The protective cover  80  includes a latch  400  (FIG. 16) to retain the handle  30  in a locked position and includes a stop  410  to limit the travel of the handle  30  in the open position. 
     Turning to FIG. 8, the interior of the cover  14  is illustrated in more detail. The cover  14  includes a bottom surface  82  including the pin pattern  18  therein. The cover  14  includes side walls  84  and an end wall  60  located near the front  11  of the socket  10 . The side walls  84  include a plurality of vertical skirts  86  thereon to provide structural rigidity. The outer latches  54  are distributed along the interior of both side walls  84 . Recesses  88  may be provided as core voids to facilitate and balance the flow of plastic compound during manufacturing. Optionally, an opening  90  may be provided in the center of the cover  14 . Center posts  92  and  94  project outward from the bottom surface  82  of the cover  14 . The center posts  92  and  94  have upper surfaces that are located proximate the main journals  34  and  36  of the leg  32  on the actuation lever  28 . The center posts  92  and  94  cooperate with the cut-outs  40  and  42  to define bearings, within which the main journals  34  and  36  rotate, while limiting movement of the leg  32  in any other direction. 
     The bottom surface  82  includes a recessed portion  96  near the back edge  83  and chamfered regions  98  and  100  to receive the upper portion of the block section  48  on the cam assembly  24 . The recessed portion  96  may be arcuately shaped to follow the contour of the dome shaped top  49  (FIG. 9) of the block section  48 . 
     FIG. 10 illustrates the bottom side of the cam assembly  24 . The cam assembly  24  may include a plurality of core voids  102  to prevent sink marks or excess shrinkage during manufacturing. Optionally, the cam assembly  24  may include beveled edges  104  to ensure adequate clearance during operation within the journaled portion  22 . Multiple pockets  106 - 108  are provided to securely engage retention barbs  120 - 123  on the wear plate  26  (FIG.  11 ). The block section  48  includes closed ends  110  and  112  and the dome shaped top  49  to define a pocket  114  that securely receives the wear plate  26 . The pocket  114  includes a recessed portion  116 , vertical walls  118  and beveled edges  119  aligned to substantially conform to the shape of the wear plate  26 . The recess  114  prevents lateral movement in the direction of arrow D by the wear plate  26  while the cam assembly  24  is moved in the direction of arrow A. 
     FIG. 11 illustrates the wear plate  26  which includes multiple retention barbs  120 - 123  integrally formed with top and side sections  124  and  126 . The top and side sections  124  and  126  rotatably receive the cam journal  38  and permit pivotal and arcuate motion of the cam journal  38  while moving the socket  10  between the open and closed positions. Optionally, the wear plate  26  may be press fit into the pocket  114 . The retention barbs  120 - 123  are provided with a width sufficient to form an interference fit securely within the pockets  106 - 108 . 
     FIG. 12 illustrates the arcuate and pivotal motions carried out by the actuation lever  28  during operation. As the actuation lever  28  is moved along the direction designated by arrow B, the leg  32  pivots about the longitudinal axis  128 , thereby causing the cam journal  38  to move about an arcuate path designated by arrow E within a vertical plane aligned perpendicular to the longitudinal axis  128 . The cam journal  38  is offset from the longitudinal axis  128  by a distance necessary to actuate the cam assembly  24 . 
     During operation, the actuation lever  28  is rotated along an arcuate path (see arrow B in FIG. 2) to cause a sliding lateral motion of the cam assembly  24  (see arrow A in FIG.  5 ), thereby causing the pusher bars  44  and slots  46  to cooperate to force the base housing  12  and cover  14  between open and closed positions. 
     Optionally, the actuation member  28  may be modified to include two or more legs  32  evenly distributed across the width of the base housing  12 . Each leg  32  would be received in corresponding cutouts, such as cutouts  40  and  42 , similarly distributed across the width of the socket. The cam assembly would include pockets, such as pocket  114 , distributed along the length of the cam assembly and configured to rotatably receive cam journals on each leg. A linkage would be provided to connect each leg to one or more handles, such as handle  30 , in order to simultaneously and synchronously rotate the legs. 
     FIG. 13 illustrates an alternative embodiment for a socket  200  having a base  212  and cover  214 . An actuation member  220  includes a handle  222  and a leg  224 . The leg  224  includes a plurality of threads  226 . FIG. 14 illustrates a cross-sectional view taken along line  14 — 14  in FIG. 13 of a portion of the socket  200 . In FIG. 14, the cover  214  and base  212  slidably engage one another, whereby the direction of motion therebetween is indicated by arrow F in FIG.  13 . The cover  214  and base  212  each include half moon shaped trough sections  216  and  218  that cooperate to define a chamber to receive the leg  224  of the actuation lever  220 . The cover  214  includes threaded recesses  219  engaging the threads  226  of the actuation member  220 . As the handle  222  of the actuation member  220  is rotated about its rotational axis, the threads  226  and  219  cooperate to move the cover  214  in the direction of arrow F. Optionally, the base  212  may include threads within trough  218 , while the threads  219  are removed from trough  216 . The actuation lever  220  achieves forward and reverse sliding movement of the cover  214  relative to the base  212  by applying a screw type force between threads  226  and  219 . 
     Alternatively, the embodiment of FIGS. 13 and 14 may be modified to include multiple threaded legs similar to leg  224 . For instance, two or three threaded legs may be evenly spaced along the width of the socket  200 , with a corresponding number of trough sections  216  and  218  similarly spaced along the width of the socket  200 . In this alternative embodiment, the handle  222  may be modified to include a linkage interconnecting all of the threaded legs. The linkage would rotate the threaded sections simultaneously and synchronously in either direction. By using multiple threaded legs, the driving forces would be more evenly distributed across the width of the socket  200 . 
     Alternatively, the embodiment of FIGS. 13 and 14 may be combined with the embodiments of FIGS. 1-12. For example, the cam assembly may be driven by a screw-type member such as the actuation member  220 . The cam assembly may be moved in a direction parallel or perpendicular to the socket longitudinal axis, or at an acute angle thereto. 
     FIG. 15 illustrates an alternative embodiment for a cam assembly  300 . The cam assembly  300  includes latch members  302  and  304  provided on either side thereof. The latches  302  and  304  are provided to retain the cam assembly  300  within the base housing. The latches  302  and  304  include shelves  306  that slidably engage corresponding structures within the base housing  14  to permit lateral side-to-side movement of the cam assembly  300 , while retaining the cam assembly  300  within the base housing  14 . 
     FIG. 16 illustrates a portion of the base housing  14  including tracks  310  within the journaled portion  312 . The tracks  310  include sidewalls  314  having latches  316  provided therein to slidably engage the latches  302  and  304  on the cam assembly  300 . While not illustrated, latches resembling latches  316  are provided in the opposite side of tracks  310 . The base housing  14  illustrated in FIG. 16 further includes pockets  320  that cooperate with posts  322  mounted on the interior of the cover  12 . FIG. 17 illustrates an interior of a cover  12  including posts  322  that are received within pockets  320 . Pockets  320  and posts  322  cooperate to prevent rotation of the cover  12  while the lever  16  is rotated and the cam assembly  24  is slid from side-to-side. 
     While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood, of course, that the invention is not limited thereto since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings. It is therefore contemplated by the appended claims to cover such modifications as incorporate those features which come within the spirit and scope of the invention.