Abstract:
A socket is provided for an IC package having a plurality of contacts. The socket includes a body mounting a plurality of terminals and having a receptacle in the top thereof for receiving the IC package with the contacts in engagement with the terminals. At least one retainer/ejector member is mounted on the socket body adjacent the receptacle for movement relative to the body from a first position retaining the IC package in the receptacle and a second position at least partially ejecting the IC package from the receptacle. An actuator member is movably mounted on the socket body. The actuator member is operatively associated with the retainer/ejector member for moving the retainer/ejector member from its first position to its second position.

Description:
FIELD OF THE INVENTION 
     This invention generally relates to the art of IC sockets and, particularly, to a retention/ejection system for an IC package mounted within the socket. 
     BACKGROUND OF THE INVENTION 
     An IC socket is used for performing burn-in tests of IC packages. In other words, an IC package is tested for a given number of hours at given, sometimes elevated, temperatures to ensure that the IC package will not fail during normal operation. Such an IC socket typically includes a dielectric socket body or housing which mounts a plurality of terminals in respective terminal-receiving passages in the body. In some sockets, first contact ends of the terminals receive respective solder balls of a ball grid array of the IC package, for instance. The opposite ends of the terminals have tails which engage circuit traces on a printed circuit board. Spring portions typically are provided intermediate the opposite contact ends of the terminals for applying contact pressure at the interconnections with the solder balls and the printed circuit board. Burn-in sockets of this type are shown in Japanese Unexamined Patent Publication Nos. Heisei 6-203926 and 9-162332. 
     During a burn-in test, it is necessary that the IC package be held by some form of retaining means whereby the respective solder balls of the package are maintained in contact with the respective contact terminals of the IC socket with sufficient pressure to overcome any oxide film on the surface of the solder balls in order to obtain reliable connections between the solder balls and contact terminals. Unfortunately, problems arise during the testing under high pressure in that the solder balls may melt quite slightly and become adhered to the contact ends of the terminals. Consequently, it may be difficult to remove the IC package from the socket after testing. The present invention is directed to solving these problems by providing an IC socket of the character described with a new and improved retainer/ejector system for holding the IC package in and ejecting the IC package from the IC socket. 
     SUMMARY OF THE INVENTION 
     An object, therefore, of the invention is to provide a new and improved socket for an IC package having a plurality of contacts. 
     In the exemplary embodiment of the invention, the IC socket includes a socket body mounting a plurality of terminals and having a receptacle in the top of the body for receiving the IC package with the contacts thereof in engagement with the terminals. At least one retainer/ejector member is mounted on the socket body adjacent the receptacle for movement relative to the body from a first position retaining the IC package in the receptacle and a second position at least partially ejecting the IC package from the receptacle. An actuator member is movably mounted on the socket body and is operatively associated with the retainer/ejector member for moving the retainer/ejector member from its first position to its second position. 
     A support frame also may be movably mounted on the socket body about the receptacle and on which the IC package is supported. The retainer/ejector member includes a retaining portion for engaging the IC package and holding the package in the receptacle. The retainer/ejector member includes an ejecting portion for engaging and moving the support frame and, thereby, at least partially ejecting the IC package. 
     As disclosed herein, the receptacle is generally rectangular and is generally centrally located in the top of the socket body. A plurality of the retainer/ejector members are spaced about the receptacle, preferably at each of the four sides of the rectangular receptacle. 
     In the preferred embodiment, each retainer/ejector member is provided in the form of an arm pivotally mounted on the socket body at a side of the receptacle and cantilevered into the receptacle when in its first or retaining position. The arm has a retaining portion near a distal end thereof for engaging the IC package and holding the package in the receptacle. The arm has an ejecting portion near a proximal end thereof adjacent the pivot point of the arm for engaging the support frame for the IC package. The actuator member is provided in the form of an actuator rim mounted to the top of the socket body substantially surrounding the receptacle and operatively associated with all of the plurality of retainer/ejector arms. 
     Other features of the invention include complementary interengaging cam means between the retainer/ejector arms and the actuator rim for moving the arms in response to movement of the rim. A plurality of springs are spaced about the actuator rim between the rim and the socket body for biasing the rim toward a retaining position and, thereby, bias the retainer/ejector arms toward their first or retaining positions. 
     Other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of this invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with its objects and the advantages thereof, may be best understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements in the figures and in which: 
     FIG. 1 is a top plan view of an IC socket embodying the concepts of the invention; 
     FIG. 2 is a fragmented vertical section taken generally along line A—A of FIG.  1  and showing an IC package in a burn-in test phase; 
     FIG. 3 is a fragmented vertical section taken generally along line B—B of FIG. 1 and, again, showing the IC package in the burn-in test phase; 
     FIG. 4 is a view similar to that of FIG. 3, but with the actuator rim depressed and the retainer/ejector arms pivoted upwardly for removing the IC package; 
     FIG. 5 is an enlarged fragmented vertical section through a portion of the IC socket to show one of the terminals interengaged between the IC package and the printed circuit board; 
     FIG. 6 is an enlarged plan view of an isolated cluster of terminal-receiving passages and terminals, looking generally in the direction of line C—C of FIG. 5; 
     FIG. 7 is a fragmented, isolated view showing the contact end of one of the terminals in engagement with a respective solder ball of the IC package; 
     FIG. 8 is an enlarged isolated section through the socket showing the interengagement between a pair of the terminals and a pair of the solder balls of the IC package; 
     FIG. 9 is an enlarged isolated section through the area of retention for a pair of the terminals in the IC socket; 
     FIG. 10 is a view similar to that of FIG. 8, but showing the bottom or tail areas of the terminals in engagement with the printed circuit board; 
     FIG. 11 is a view similar to that of FIG. 8, with the IC package and solder balls elevated above the terminals; 
     FIG. 12 is an enlarged isolated section through the socket in the area of one of the retainer/ejector arms, showing the arm in its retaining position; 
     FIG. 13 is a view similar to that of FIG. 12, but showing the retainer/ejector arm partially moved away from its retaining position; 
     FIG. 14 is a view similar to that of FIGS. 12 and 13, but showing the arm moved all of the way to its ejecting position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings in greater detail, and first to FIGS. 1-3, an IC socket for performing burn-in tests is generally designated  1 . The socket includes a socket body  2  which is an assembly formed by an outer cup-shaped housing  3  defining a rectangular center opening  3   a  and an inner housing  4  received in the center opening. Inner housing  4  is formed by three rectangular housing segments  4   a ,  4   b  and  4   c  which are stacked within center opening  3   a  of outer housing  3 . 
     A printed circuit board, generally designated  5 , is fixed by four bolts  8  to the lower surface of outer housing  3 . Housing segments  4   a ,  4   b  and  4   c  are fixed within center opening  3   a  of outer housing  3  by a stepped bolt  10 . The stepped bolt extends upwardly through printed circuit board  5  and into the outer housing. 
     An actuator rim  12  is positioned onto a top surface  14  of outer housing  3 . The actuator rim has a square center opening, generally designated  16 , and is biased upwardly by eight coil springs  18  sandwiched between the actuator rim and the outer housing. The actuator rim is held down onto the outer housing by the engagement of hooks  20   a  (FIG. 2) of a plurality of latch arms  20  fixed to opposite sides of outer housing  3 . Therefore, actuator rim  12  is resilient held on top of the housing and can be depressed against the biasing of springs  18 , while hooks  20   a  of latch arms  20  limit movement of the cover upwardly or away from the housing. While FIGS. 2 and 3 show actuator rim  12  biased upwardly by springs  18 , FIG. 4 shows the cover pushed downwardly in the direction of arrow “X”, as will be described in greater detail hereinafter. 
     Center opening  3   a  of outer housing  3  is provided with tapered guiding surfaces  22  at the four corners of the opening for guiding the corners of a rectangular IC package  24  into the top of the opening. At this point, it should be understood that such terms as “top”, “bottom”, “upwardly”, “downwardly” and the like are used herein to provide a clear and concise description and understanding of the invention in view of the orientation of IC socket  1  in the drawings. However, it should be understood that such terms herein and in the claims hereof are not intended to be limiting. 
     FIGS. 2-4 show a terminal area, generally designated  26 , somewhat schematically by phantom/solid line cross-hatching, because the details would be too fine to show in these figures. Suffice it to say, it can be seen that the terminal areas are generally along each edge of housing segments  4   a ,  4   b  and  4   c  of inner housing  4 . More particularly, referring to FIG. 5, a plurality of terminals, generally designated  28 , are mounted in a respective plurality of terminal-receiving passages  30  which extend in aligned fashion through the stacked inner housing segments  4   a ,  4   b  and  4   c . FIG. 6 shows a cluster of four terminal-receiving passages and respective terminals to illustrate that all of the terminals are in alternating perpendicular orientations relative to adjacent terminals about the four edges of the stacked housing segments. As seen in FIG. 5, terminal-receiving passages  30  are open at the top of upper housing segment  4   a  and at the bottom of lower housing segment  4   c.    
     Each terminal  28  includes a top contact end  32  and a bottom contact end  34  which terminates in a tail portion  34   a . Each terminal includes an enlarged intermediate retention section  36  for fixing the terminal in its respective passage  30 , as described below. Each terminal includes a first or top spring section  38  which extends between retention section  36  and top contact end  32 . A second or bottom spring section  40  extends between retention section  36  and bottom contact section  34 . Each terminal is stamped or blanked from conductive sheet metal material, and it can be seen that spring sections  38  and  40  are stamped in a sinuous or wave-spring configuration. The spring sections generally have the same cross-dimensions, but it can be seen that top spring section  38  is longer than bottom spring section  40 . Therefore, the top spring section is more resilient than the bottom spring section and, as a result, the top spring section will exert a lesser longitudinal force toward top contact end  32  than the forces applied by bottom spring section  40  on bottom contact end  34 / 34   a . Referring to FIG. 9 in conjunction with FIG. 5, it can be seen that retention section  36  of each terminal  28  is enlarged laterally to define a pair of outwardly projecting flanges  36   a  which are sandwiched between housing segments  4   b  and  4   c  of inner housing  4 . This fixes the terminals within their respective terminal-receiving passages  30  in the housing segments. 
     Referring to FIG. 7 in conjunction with FIG. 5, top contact end  32  of each terminal  28  is bifurcated at the distal end thereof to form a recessed area  42  between a pair of symmetrical contact portions  44 . The contact portions have oblique faces  46  which extend to horizontal stepped faces  48  which, in turn, terminate at pointed edges  50 . The pointed edges of each contact end  32  engage a respective one of a plurality of solder balls  52  of IC package  24 . FIG. 8 shows how contact ends  32  of terminals  28  yield downwardly in the direction of arrow “Y” when pressure is applied by IC package  24  and solder balls  52  onto the contact ends. FIG. 11 shows the IC package and solder balls lifted off of contact ends  32  of terminals  28 , whereupon the terminals return to their unstressed conditions. 
     FIG. 10 shows bottom contact ends  34  and tail portions  34   a  of three terminals in engagement with a top surface  5   a  of printed circuit board  5 . It can be seen that the bottom contact ends have been biased upwardly an amount indicated by arrows “C” under the resiliency of bottom spring sections  40  (FIG. 5) of the terminals. Tail portions  34   a  will be in engagement with circuit traces on top surface  5   a  of the printed circuit board. 
     Referring to FIG. 12 in conjunction with FIGS. 2 and 3, a rectangular support frame  60  has a rectangularly shaped central opening  62  within which IC package  24  is mounted and rests on a seating surface  64  about the inside of the support frame. A bottom peripheral flange  66  depends from the support frame into a groove  68  in a top surface of upper housing segment  4   a  of inner housing  4 . Support frame  60  is disposed within an upstanding portion  70  of outer housing  3 . Therefore, support frame  60  can move up and down with IC package  24 . 
     Still referring to FIG. 12 in conjunction with FIGS. 2 and 3, a retainer/ejector arm  72  is pivotally mounted at point  74  to upstanding portion  70  of the outer housing. One of the retainer/ejector arms  72  is disposed at each of the four sides of center opening  16 . Arm  72  is shown in FIG. 12 in a first or retaining position whereby a retaining portion  72   a  at a distal end of the arm is disposed on top of IC package  24  at an edge thereof to hold the IC package in the IC socket. The retainer/ejector arm also includes an ejecting portion or surface  72   b  at a proximal end of the arm near pivot point  74 . As will be seen hereinafter, ejecting surface  72   b  is positioned for engaging support frame  60  to raise the support frame and eject the IC package from the socket. Still further, each retainer/ejector arm  72  includes an abutment surface  72   c  for a purpose to be described hereinafter. Therefore, it can be seen that each retainer/ejector arm is cantilevered from pivot point  74  out over center opening  3   a  in outer housing  3  as well as into the center opening within actuator rim  12 . 
     Generally, and still referring to FIG. 12, complementary interengaging cam means, generally designated  80 , are disposed between each retainer/ejector arm  72  and actuator rim  12  for moving the retainer/ejector arms in response to movement of the actuator rim. More particularly, a cam roller  82  is rotatably mounted on a shaft  84  on each retainer/ejector arm  72 . Actuator rim  12  has a cam shoulder  86  facing the cam roller. Before proceeding with the operation of the system in relation to FIGS. 13 and 14, FIG. 12 shows that outer housing  3  has an integral, upstanding spring arm  88  which includes an upper distal end  88   a  in the path of rotation of surface  72   c  of retainer/ejector arm  72 . 
     The operation of the retaining/ejecting system of the invention now will be described in relation to FIGS. 12-14. Referring first to FIG. 12, the retaining position of retainer/ejector arm  72  is shown. In this position, springs  18  bias actuator rim  12  upwardly which causes a surface  90  on the actuator rim to engage cam roller  82 . This engagement causes retainer/ejector arm  72  to be forced inwardly and downwardly so that its distal end  72   a  engages the top of IC package  24  at the edge thereof to hold the IC package within the socket. 
     When it is desired to eject IC package  24  from the socket, pressure is exerted onto actuator rim  12  in the direction of arrow “X” as seen in FIG.  13 . This causes cam shoulder  86  on the actuator rim to engage the top of cam roller  82  and rotate retainer/ejector arm  72  upwardly about pivot  74 . This lifts retaining surface  72   a  of the arm off of the IC package. It can be seen that cam roller  82  has entered a recessed area  92  in the actuator rim which is provided to accommodate rotating movement of the cam roller. 
     Referring to FIG. 14, further downward movement of actuator rim  12  causes further rotation of retainer/ejector arm  72  upwardly about pivot  74  until the arm attains a substantially vertical orientation, as shown. This further movement effects two functions. First, ejecting surface  72   b  of the arm engages a shoulder  94  of support frame  60  and lifts the support frame upwardly an amount as indicated by arrows  96 . Since IC package  24  is mounted on support frame  60 , the IC package also is lifted upwardly and at least partially ejected from the socket. Second, surface  72   c  of retainer/ejector arm  72  engages upper distal end  88   a  of spring arm  88  to cock the spring arm and spring load the retainer/ejector arm. Therefore, when pressure on actuator rim  12  is removed, spring arm  88  is effective to bias retainer/ejector arm  72  back downwardly as springs  18  bias the actuator rim upwardly. 
     The amount of upward ejecting movement of support frame  60  and, thereby, IC package  24  as indicated by arrows  96  in FIG. 14, is sufficient to accommodate the yielding of contact ends  32  of terminals  28  as described in relation to FIGS. 7,  8  and  11 . In addition, the amount of upward ejecting movement also is sufficient to break any adhesion between contact ends  32  of the terminals and solder balls  52 , particularly at pointed edges  50  (FIG. 7) of the terminals. 
     It will be understood that the invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.