Abstract:
A retention mechanism ( 6, 6 ′) for an LGA package assembly ( 1, 1 ′) consists of a spring clip ( 60, 60 ′) and a lever ( 62, 62 ′) both attached to a heat sink ( 5, 5 ′). The spring clip has a biasing strip ( 612, 612 ′) and a pair of opposite engaging legs ( 610, 610 ′). The lever includes an arcuate section ( 680, 680 ′) positioned beneath the biasing strip, whereby the lever is rotatable from a vertical position where the arcuate section is contained in a plane parallel with the biasing strip to a horizontal position where the arcuate section is contained in a plane perpendicular to the biasing strip and engages with the biasing strip. When the lever is rotated to the horizontal position, the biasing strip is biased upwardly to cause the engaging legs to abut against a bottom surface ( 22 ) of a PCB ( 2 ), whereby the components of the LGA package assembly are mechanically and electrically connected to one another.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an IC (Integrated Circuit) package assembly, and particularly to an LGA (Land Grid Array) package assembly having a retention mechanism for mechanically and electrically securing the components of the LGA package assembly to one another. 
     2. Description of Prior Art 
     IC packages having leads arranged in a land grid array (LGA) are well known as LGA packages. Connectors for removably mounting an LGA package on a PCB (Printed Circuit Board) are known as LGA sockets. An LGA socket comprises a substantially flat insulative housing defining an array of passageways with electrical contacts received therein corresponding with the array of leads of the LGA package. Each contact has a pair of free ends oppositely projecting beyond external surfaces of the socket housing for respectively engaging with corresponding contact pads on a bottom surface of the LGA package and on a top surface of the PCB. To dissipate the heat generated by an IC chip incorporated in the LGA package, a heat sink is commonly applied. 
     Different methods are disclosed by the prior art for clamping the LGA package, the LGA socket and the PCB together, thereby establishing an electrical connection between the contacts of the LGA socket and corresponding contact pads of the LGA package and the PCB. U.S. Pat. No. 4,906,194 discloses an LGA package assembly consisting of an upper support plate, an LGA package, an LGA socket, a PCB, an insulator, and a lower support plate. The components of the LGA package assembly are fastened to each other by a plurality of threaded screw members sequentially extending through bores defined in each component, which is laborious and tedious. U.S. Pat. No. 5,847,928 discloses another LGA package assembly consisting of a heat sink, an LGA package, an LGA socket and a PCB. The components are fastened together by a clip disposed on a bottom side of the PCB which has two upwardly extending arms inserted in aligned apertures of the PCB and the heat sink. One problem with this design is that the retention force of the clip for fastening the components of the assembly together is not sufficient enough to prevent physical separation therebetween when the assembly is subject to external shock and vibration. Such a physical separation may result in broken circuits between the LGA package and the PCB, thereby adversely affecting the operation of the LGA package assembly. 
     Hence, an improved LGA package assembly is desired to overcome the aforesaid disadvantages of the prior art. 
     SUMMARY OF THE INVENTION 
     Accordingly, one object of the present invention is to provide an LGA package assembly having a retention mechanism for securely connecting components thereof to one another. 
     Another object of the present invention is to provide a retention mechanism for an LGA package assembly for reliably connecting an LGA package to a PCB. 
     A further object of the present invention is to provide a retention mechanism for an LGA package assembly which is easy to assemble and disassemble. 
     In order to achieve the objects set forth, an LGA package assembly in accordance with the present invention comprises a PCB, a socket mounted on the PCB, an LGA package coupled to the socket, a heat sink positioned on the LGA package, and a retention mechanism for mechanically and electrically assembling the above components together. Preferably, a metal support plate may be attached to a bottom surface of the PCB for strengthening the PCB, and an elastomer may be sandwiched between the heat sink and the LGA package and also between the PCB and the support plate. 
     The retention mechanism consists of a spring clip and a lever. The spring clip has a biasing strip attached to a planar substrate of the heat sink and substantially parallel with the substrate, and a pair of engaging legs on opposite ends of the biasing strip, each engaging leg having an engaging toe horizontally extending from a free end thereof. The lever includes an actuation beam attached to the heat sink and extending in a direction perpendicular to the biasing strip of the spring clip. An arcuate section is formed on the actuation beam and is positioned beneath the biasing strip of the spring clip, whereby the lever is rotatable from a vertical position where the arcuate section is contained in a plane parallel with the biasing strip of the spring clip to a horizontal position where the arcuate section is contained in a plane perpendicular to the biasing strip of the spring clip and engages with the biasing strip of the spring clip. 
     When the lever is rotated to the horizontal position to engage with the biasing strip of the spring clip, the biasing strip is biased upwardly to cause the engaging toes of the spring clip to abut against the bottom surface of the PCB or the support plate, whereby the heat sink is securely attached to the PCB and whereby a reliable electrical connection is established between oppositely projecting contact portions of contacts of the socket and corresponding contact pads on a bottom surface of the LGA package and on a top surface of the PCB. 
     Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded, perspective view of an LGA package assembly in accordance with a first embodiment of the present invention; 
     FIG. 2 is a perspective view of a spring clip shown in FIG. 1; 
     FIG. 3 is a perspective view of a lever shown in FIG. 1; 
     FIG. 4 is an assembled view of the LGA package assembly of FIG. 1 with the lever in a vertical position where the LGA package assembly is in an unlocked position; 
     FIG. 5 is a front view of FIG. 4; 
     FIG. 6 is an assembled view of the LGA package assembly of FIG. 1 with the lever in a horizontal position where the LGA package assembly is in a locked position; 
     FIG. 7 is a front view of FIG. 6; 
     FIG. 8 is an exploded, perspective view of an LGA package assembly in accordance with a second embodiment of the present invention; 
     FIG. 9 is a perspective view of a spring clip shown in FIG. 8; 
     FIG. 10 is a perspective view of a lever shown in FIG. 8; 
     FIG. 11 is an assembled view of the LGA package assembly of FIG. 8 with the lever in a vertical position where the LGA package assembly is in an unlocked position; 
     FIG. 12 is a front view of FIG. 11; 
     FIG. 13 is an assembled view of the LGA package assembly of FIG. 8 with the lever in a horizontal position where the LGA package assembly is in a locked position; and 
     FIG. 14 is a front view of FIG.  13 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     For facilitating understanding, like components are designated by like reference numerals throughout the various embodiments of the invention as shown in the various drawing figures. 
     Reference will now be made to the drawing figures to describe the present invention in detail. 
     Referring to FIG. 1, an LGA package assembly  1  in accordance with a first embodiment of the present invention comprises a PCB  2 , an LGA socket  3  for being mounted on the PCB  2 , an LGA package  4  with an LGA chip (not shown) incorporated therein for being received in the LGA socket  3 , a heat sink  5  for dissipating heat generated by the LGA chip of the LGA package  4 , and a retention mechanism  6  consisting of a spring clip  60  and a lever  62  for attaching the heat sink  5  to the LGA package  4  and for reliably connecting the LGA package  4  with the PCB  2  via the LGA socket  3 . Preferably, a metal support plate  7  may be positioned below the PCB  2  for strengthening the PCB  2 . Elastomers  8  and  9  may be respectively placed between the PCB  2  and the support plate  7  and between the heat sink  5  and the LGA package  4  to prevent separation therebetween under shock and vibration. Additionally, the elastomers  8  and  9  act as a strain-relief by uniformly distributing forces exerted on the LGA package  4  and the PCB  2  along the area of contact with the respective LGA package  4  and the PCB  2 . 
     The LGA package  4  comprises a plurality of contact pads (not shown) on a bottom surface thereof arranged in an array corresponding to leads (not shown) of the LGA chip incorporated therein. Corresponding to the contact pads of the LGA package, a plurality of contact pads  20  is also provided on a top surface  26  of the PCB  2 . To interconnect the LGA package  4  with the PCB  2 , the LGA socket  3  retains a plurality of contacts  30  therein each having oppositely projecting contact portions  32  and  34  for respectively connecting with corresponding contact pads of the LGA package  4  and the PCB  2 . A rectangular cavity  36  is defined in the LGA socket  3  for receiving the LGA package  4  therein. 
     The heat sink  5  includes a planar substrate  50  to be positioned on the LGA package  4  and a plurality of heat dissipating fins  52  upwardly extending from the substrate  50 . A first pair of spaced protrusions  56  is formed on a top surface  54  of the substrate  50  proximate each lateral side of the substrate  50 . The substrate  50  further includes a pair of wings  57  respectively extending outward from opposite lateral sides thereof. Each wing  57  forms a second pair of spaced protrusions  58  proximate a free end thereof. The second pair of protrusions  58  is spaced a distance equal to that between the first pair of protrusions  56 . An engaging aperture  59  is defined in the substrate  50  between the first and second pairs of protrusions  56  and  58  and proximate the first pair of protrusions  56 . 
     As is clearly shown in FIG. 2, the spring clip  60  of the retention mechanism  6  is integrally formed by stamping and bending a metal sheet. The spring clip  60  includes a pair of parallel, laterally extending spring members  61  which are maintained in spaced-apart relation by a pair of integral, longitudinally extending bridges  63 . Each spring member  61  includes a pair of engaging legs  610 , a biasing strip  612  between the engaging legs  610 , and a pair of opposed bent portions  614  interconnecting the engaging legs  610  with adjacent ends of the biasing strip  612 . Each bent portion  614  has a reversed U-shape for providing the spring member  61  with resiliency. The pair of engaging legs  610  of each spring member  61  has a pair of respective engaging toes  616  extending away from each other. The biasing strip  612  has a yoke  618  downwardly extending from an inner edge thereof. The bridges  63  comprise a pair of respective flanges  630  extending from upper edges thereof toward each other. One of the bridges  63  further includes an outwardly extending catch  632  forming an inwardly directed hook  634  at a free end thereof, whereby the corresponding flange  630  is divided into two sections. 
     Referring to FIG. 3, the lever  62  of the retention mechanism  6  is adapted to be used in cooperation with the spring clip  60 . Correspondingly, the lever  62  includes a pair of opposite lateral beams  64 , a handling beam  66  interconnecting the lateral beams  64 , and a pair of actuation beams  68  extending from respective free ends of the lateral beams  64  toward each other. The handling beam  66  has a U-shaped latch  660  contained in a plane perpendicular to the lateral beams  64  for resting on the hook  634  of the catch  632  of the spring clip  60 . Each actuation beam  68  includes an arcuate section  680  contained in a plane parallel with that of the U-shaped latch  660 , and a horizontal free end section  682  for extending through the yoke  618  of the spring clip  60 . 
     In assembly, as is illustrated in FIG. 4, the LGA package  4  is received in the rectangular cavity  36  of the LGA socket  3 . The assembled LGA package  4  and socket  3  are then mounted on the PCB  2 , and the heat sink  5  is lowered onto the LGA package  4  with the elastomer  9  sandwiched therebetween. The support plate  7  is attached to a bottom surface  22  of the PCB  2  with the elastomer  8  sandwiched therebetween. The spring clip  60  and the lever  62  of the retention mechanism  6  are then assembled together with the actuation beams  68  of the lever  62  positioned below the biasing strips  612  of the spring clip  60  and with the free end sections  682  of the actuation beams  68  of the lever  62  extending into corresponding yokes  618  of the spring clip  60 . The assembled retention mechanism  6  is finally attached to the heat sink  5  with the lever  62  in a vertical position where the arcuate sections  680  of the lever  62  are contained in a horizontal plane parallel with the substrate  50  of the heat sink  5 . The actuation beams  68  of the lever  62  are retained by the first and second pairs of spaced protrusions  56  and  58  of the heat sink  5  and the arcuate sections  680  are received in a space defined between the first and second pairs of the protrusions  56  and  58 , whereby lateral and longitudinal movements of the actuation beams  68  are prevented. The yokes  618  of the spring clip  60  are partially inserted into corresponding engaging apertures  59  of the substrate  50  with the inserted free end sections  682  of the actuation beams  68  of the lever  62  extending therethrough. The flanges  630  of the bridges  63  abut against the top surface  54  of the substrate  50 , and the engaging legs  610  of the spring clip  60  sequentially extend into aligned holes  24  and  74  (only three visible) respectively defined in the PCB  2  and the support plate  7 . 
     FIGS. 4 and 5 show an assembled view of the LGA package assembly  1  of the first embodiment in an unlocked position where the lever  62  is retained in a vertical position. In this unlocked position, the arcuate sections  680  of the actuation beams  68  of the lever  62  are contained in a plane parallel with the biasing strips  612  of the spring clip  60 , and the engaging toes  616  of the engaging legs  610  of the spring clip  60  project beyond the bottom surface  72  of the support plate  7 , whereby the opposite contact portions  32  and  34  of the contacts  30  of the LGA socket  3  are not brought into reliable electrical connection with corresponding contact pads of the LGA package  4  and the PCB  2 . 
     FIGS. 6 and 7 show an assembled view of the LGA package assembly  1  of the first embodiment in a locked position where the lever  62  is rotated from the vertical position shown in FIGS. 4 and 5 to a horizontal position. During the rotation process of the lever  62 , the yokes  618  of the spring clip  60  are vertically movable in the corresponding engaging apertures  59 . In the locked position, the arcuate sections  680  of the actuation beams  68  of the lever  62  are contained in a plane perpendicular to the biasing strips  612  of the spring clip  60  and engage with the biasing strips  612 , whereby the biasing strips  612  are biased upwardly to cause the engaging toes  616  of the engaging legs  610  to abut against the bottom surface  72  of the support plate  7 . Consequently, a spring force is exerted by the spring clips  60  on the heat sink  5  via the actuation beams  68  of the lever  62 , which is further transferred by the heat sink  5  to the LGA package  4 , the LGA socket  3  and the PCB  2 , thereby pressing the opposite contact portions  32  and  34  of the contacts  30  of the LGA socket  3  into reliable electrical connection with corresponding contact pads of the LGA package  4  and the PCB  2 . 
     An LGA package assembly  1 ′ in accordance with a second embodiment of the present invention is illustrated in FIGS. 8-14. The configuration of the second embodiment is similar to that of the first embodiment except for the retention mechanism  6 ′ and the heat sink  5 ′. Therefore, only the retention mechanism  6 ′ and the heat sink  5 ′ of the second embodiment will be described in detail hereinafter. 
     As is clearly shown in FIG. 9, the spring clip  60 ′ of the second embodiment is similar to the spring clip  60  of the first embodiment except that the downwardly extending yoke  618  of the spring clip  60  is replaced by a pair of horizontally and inwardly extending fingers  618 ′, and the one catch  632  is replaced by a pair of catches  632 ′. 
     Referring to FIG. 10, the lever  62 ′ of the second embodiment comprises a pair of opposite lateral beams  64 ′, an actuation beam  68 ′ interconnecting the lateral beams  64 ′, and a handling beam  66 ′ parallel with the actuation beam  68 ′. A pair of actuation sections  680 ′ is provided by the actuation beam  68 ′. The handling beam  66 ′ comprises a pair of longitudinal sections  662  respectively extending from free ends of the lateral beams  64 ′ toward each other. Each longitudinal section  662  has an enlarged end  664  defining a threaded hole  666  therein. A tab  667  defining a pair of engaging holes  668  in alignment with corresponding threaded holes  666  of the longitudinal sections  662  is secured to the longitudinal sections  662  by a pair of screws  669  for facilitating handling by a user. 
     Referring to FIGS. 8,  11  and  13 , corresponding to the configuration of the spring clip  60 ′ and the lever  62 ′, the heat sink  5 ′ defines a central groove  51  within the plurality of fins  52 ′ and forms a pair of spaced protrusions  56 ′ proximate each lateral side thereof. A groove  53  is defined between each pair of protrusions  56 ′ aligned with the central groove  51  for cooperatively receiving the actuation beam  68 ′ of the lever  62 ′. Each protrusion  56 ′ further defines an upwardly exposed slot  55  proximate the groove  53  for receiving a corresponding finger  618 ′ of the spring clip  60 ′. 
     In assembly, the lever  62 ′ is attached to the heat sink  5 ′ in a vertical position with a middle section of the actuation beam  68 ′ thereof received in the aligned grooves  51  and  53  and with the arcuate sections  680 ′ located beside the pair of protrusions  56 ′ and contained in a plane parallel with a substrate  50 ′ of the heat sink  5 ′. The spring clip  60 ′ is then extended into an inner space defined by the beams  64 ′,  66 ′,  68 ′ with the fingers  618 ′ thereof engaging with corresponding slots  55  of the protrusions  56 ′ and with flanges  630 ′ thereof abutting against a top surface  54 ′ of the substrate  50 ′ of the heat sink  5 ′. Engaging legs  610 ′ of the spring clip  60 ′ sequentially extend through aligned holes  24  and  74  of the respective PCB  2  and the support plate  7 . 
     FIGS. 11 and 12 show an assembled view of the LGA package assembly  1 ′ of the second embodiment in an unlocked position where the lever  62 ′ is retained in a vertical position. In this unlocked position, the arcuate sections  680 ′ of the actuation beam  68 ′ of the lever  62 ′ are contained in a plane parallel with that of the biasing strips  612 ′ of the spring clip  60 ′, and the engaging toes  616 ′ of the engaging legs  610 ′ of the spring clip  60 ′ project beyond the bottom surface  72  of the support plate  7 , whereby the opposite contact portions  32  and  34  of the contacts  30  of the LGA socket  3  are not brought into reliable electrical connection with corresponding contact pads of the LGA package  4  and the PCB  2 . 
     FIGS. 13 and 14 show an assembled view of the LGA package assembly  1 ′ of the second embodiment in a locked position where the lever  62 ′ is rotated from the vertical position shown in FIGS. 11 and 12 to a horizontal position. During the rotation process of the lever  62 ′, the slots  55  of the protrusions  56 ′ allow vertical movements of the biasing strips  612 ′ of the spring clip  60 ′. In the locked position, the arcuate sections  680 ′ of the actuation beam  68 ′ of the lever  62 ′ are contained in a plane perpendicular to that of the biasing strips  612 ′ of the spring clip  60 ′ and engage with the biasing strips  612 ′, whereby the biasing strips  612 ′ are biased upwardly to cause the engaging toes  616 ′ of the engaging legs  610 ′ of the spring clip  60 ′ to abut against the bottom surface  72  of the support plate  7 . Consequently, a spring force is exerted by the spring clips  60 ′ on the heat sink  5 ′ via the actuation beams  68 ′ of the lever  62 ′, which is further transferred by the heat sink  5 ′ to the LGA package  4 , the LGA socket  3  and the PCB  2 , thereby pressing the opposite contact portions  32  and  34  of the contacts  30  of the LGA socket  3  into reliable electrical connection with corresponding contact pads of the LGA package  4  and the PCB  2 . 
     Although the LGA package assembly  1 ,  1 ′ of the present invention is disclosed to include a retention mechanism  6 ,  6 ′, a heat sink  5 ,  5 ′, a pair of elastomers  8  and  9 , an LGA package  4 , an LGA socket  3 , a PCB  2  and a support plate  7 , it should be understood that the use of the elastomers  8  and  9  and the support plate  7  are optional. Without these optional elements, the engaging toes  616 ,  616 ′ of the spring clip  60 ,  60 ′ will abut against the bottom surface  22  of the PCB  2  rather than the support plate  7 . In addition, the spring clip  60 ,  60 ′ may only include one spring member  61 ,  61 ′ without departing from the true spirits of the present invention. 
     It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.