Patent Publication Number: US-6699057-B2

Title: Land grid array connector assembly

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the art of electrical connectors, and more particularly to a land grid array connector assembly having a securing mechanism for securing a land grid array (LGA) package therein. 
     2. Description of the Prior Art 
     A land grid array (LGA) connector is commonly used in the electronic transmission field for accommodating an LGA package therein, and establishing electrical connection between the LGA package and a substrate such as a printed circuit board (PCB) on which the connector is mounted). U.S. Pat. Nos. 5,344,334, 5,302,853, 4,682,790, 4,621,884, and 4,504,105 disclose several conventional LGA sockets. As can be seen from FIGS. 8 and 9, one kind of conventional LGA connector assembly  9  typically includes a low profile insulative housing  91  and a securing mechanism attached to the housing  91 . The securing mechanism comprises a frame  92 , a pressing plate  93  pivotally attached to one end beam of the frame  92  for pressing and securing the housing  91  in the frame  92 , and a lever  94  movably connected to an opposite end beam of the frame  92  for generating a downward pressing force to press the pressing plate  93  toward the housing  91 . 
     The lever  94  comprises an operation handle  942  located corresponding to a lateral beam of the frame  92 , a locating portion  941  perpendicularly connecting with the handle  942 , and an offset camshaft  943  integrally bending from a middle portion of the locating portion  941 . The camshaft  943  is adapted to engage with a hook  931  formed at a free end of the pressing plate  93 . The handle  942  can rotate relative to the frame  92  between a 0-degree-angle position in which the pressing plate  93  is at an open state with the hook  931  being free from the camshaft  943 , and a 180-degree-angle position where the pressing plate  93  is at a closed state with the hook  931  being pressed and located by the camshaft  943 . A pair of spaced locating blocks  921  is formed on said opposite end beam of the frame  92 . The blocks  921  define a pair of locating slots  922  therein respectively, the locating slots  922  pivotably accommodating the locating portion  941  therein. Each slot  922  spans upwardly and inwardly along the block  921  from a lowest portion of the slot  922  to a highest portion of the slot  922 . Ideally, when the handle  942  is at the 0-degree-angle position, the locating portion  941  should be positioned at the lowest portions of the slots  922 , so that the camshaft  943  is completely free from the hook  931 . Then when the handle  942  is rotated to the 180-degree-angle position, the locating portion  941  should be moved to the highest portions of the slots  922 , so that the hook  931  is fully pressed and accurately located by the camshaft  943 . 
     However, in actual use, when the handle  942  is at the 0-degree-angle position, the locating portion  941  may be displaced from the lowest portions and instead be located at intermediate positions between the lowest and highest portions. Thus, when the handle  942  is rotated from the 0-degree-angle position toward the 180-degree-angle position, the locating portion  941  slides along the slots  922  from the intermediate position, and may reach the highest portions prior to the handle  942  reaching the 180-degree-angle position. When this happens, the locating portion  941  cannot continue any further along the slot  922  since it has reached the highest portion of the slot  922 , and the handle  942  is restrained from reaching the 180-degree-angle position. As a result, the camshaft  943  fails to generate sufficient downward pressing force on the hook  931 , and the pressing plate  93  cannot be pressed to its correct closed state. The housing  9  is thus liable to be inaccurately and unreliably located. 
     An improved land grid array connector assembly which overcomes the above-mentioned shortcomings is desired. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention is to provide a land grid array connector assembly having a securing mechanism for accurately and securely retaining an LGA package onto a connector housing of the connector assembly. 
     Another object of the present invention is to provide a securing mechanism attached to a land grid array connector to accurately retain an LGA package in the land grid array connector. 
     In order to achieve the objects set forth, a land grid array connector assembly in accordance with the present invention includes an insulative housing and a securing mechanism attached to the housing. The securing mechanism comprises a frame surrounding the housing, a pressing plate movably attached to one beam of the frame, and an actuating lever pivotally attached to another opposite beam of the frame. The frame has an opening for receiving the housing therein, the lever can rotate between an open position and a closed position relate to the frame, and can generate a downward pressing force to a hook of the plate thereby locating the housing in the opening of the frame. 
     The frame further comprise a pair of locating blocks formed on one beam thereof, each block defines a locating slot for receiving a locating portion of the lever. The slot extends upwardly and inwardly toward the opening of the frame thereby forming a slantwise groove which has a lowest portion and a highest portion. A tongue portion is formed on the beam of the frame beside the locating block and extends in a direction substantially the same as the extending direction of the slot. A lower surface of the tongue portion is a continuous arc surface which can generate a pushing force which is adapted to keep the locating portion of the lever at the lowest portion of the slot when the lever is at an open position. Alternatively, the lower surface of the tongue also can form two continuous arcs jointed by a projection protruded from a middle portion of the surface, which can locate the locating portion of the lever either at the lowest portion or the highest portion of the slot. 
    
    
     Other objects, advantages and novel features of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of a land grid array connector assembly in accordance with a preferred embodiment of the present 
     FIG. 2 is an assembled view of FIG. 1, showing the connector in a closed position; 
     FIG. 3 is similar to FIG. 4, but showing the locating portion of the lever at a lowest portion of the slot, the connector assembly thus being in an open position; 
     FIG. 4 is a cross-sectional view taken along line IV—IV of FIG. 2, showing a locating portion of a lever at a highest portion of a slot of a frame; 
     FIG. 5 is an isometric view of a land grid array connector assembly in accordance with an alternative embodiment of the present invention, showing the connector assembly in a closed position; 
     FIG. 6 is similar to FIG. 4, but showing the locating portion of the lever at a lowest portion of the slot, the connector assembly thus being in an open position; 
     FIG. 7 is a cross-sectional taken along line VII—VI of FIG. 5, showing a locating portion of a lever at a highest portion of a slot of a frame; 
     FIG. 8 is an exploded, isometric view of a conventional land grid array connector assembly; and 
     FIG. 9 is an assembled view of FIG. 8, showing the connector assembly in a closed state. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiments of the present invention. 
     Referring to FIGS. 1 and 2, a land grid array (LGA) connector assembly  1  in accordance with the preferred embodiment of the present invention is illustrated. The connector assembly  1  comprises an insulative housing  2  having electrical terminals (not shown in the FIGS.) received therein for electrically connecting an LGA chip to a printed circuit board (PCB, not shown in the FIGS.). The LGA chip commonly has a low profile configuration, and is pressed onto a top surface of the housing  2  thereby establishing electrical contact with the terminals of the housing  2 . The connector assembly  1  further comprises a securing mechanism attached to the housing  2 , for securing the housing  2  on the PCB and locating the LGA chip onto the housing  2 . In the preferred embodiment, the securing mechanism includes three main elements: a frame  3 , a pressing plate  4  functioning as a pressing member, and an actuating lever  5 . The structures and functions of the three main elements are described in detail as follows, with reference to the corresponding FIGS. 
     The frame  3  has a generally rectangular configuration, and includes a first beam  30 , a second beam  31 , a third beam  32  opposite from the first beam  30 , and a fourth beam  33  opposite from the second beam  31 . The four beams  30 ,  31 ,  32 ,  33  cooperatively define a central opening therebetween, the opening being dimensioned to fit the housing  2  therein. As can be discerned from FIGS. 1 and 2, the housing  2  has been located in the opening, and the opening is therefore not visible. The first beam  30  and the third beam  32  each define a pair of spaced locating holes  34  therein, for receiving a pair of locating pins (not shown in the FIGS.) to secure the frame  3  onto the PCB. The first beam  30  forms a pair of locating blocks  301  at junctions with the second beam  31  and the fourth beam  33  respectively. Each block  301  defines a locating slot  302  therein. The slot  302  spans inwardly and upwardly in a slantwise direction perpendicular to the first beam  30  from a lowest portion  3020  of the slot  302  to a highest portion  3022  of the slot  302 . A pair of spaced tongue portions  303  is provided on the first beam  30 . Each tongue portion  303  projects from a top surface of the first beam  30  between a corresponding locating hole  34  and a corresponding locating block  301 , in a direction substantially the same as a direction spanned by an adjacent slot  302 . Each tongue portion  303  forms a locating end  3030  at a free end thereof. Referring to FIGS. 3 and 4, in the preferred embodiment, each tongue portion  303  has a curved lower surface  3032  configured as a continuous concave arc. The function of the lower surface  3032  is described in detail below. The first beam  30  also has a notched portion at a middle thereof, the notched portion defining a recess  306  whose function is described below. 
     The pressing plate  4  is made of hard material. For example, the pressing plate  4  may be stamped and bent from a sheet of metal. The pressing plate  4  is movably attached to the frame  3  by securing a pair of latches  42  formed at one end of the pressing plate  4  in corresponding receiving holes  320  defined in the third beam  32  of the frame  3 . The pressing plate  4  has a pressing portion  41  formed at an opposite end thereof. The pressing portion  41  has a distal hook  411 , which is adapted to be located in the recess  306  of the first beam  30  when the pressing plate  4  is moved to a closed position. 
     The actuating lever  5  is pivotally attached to the frame  3 . The actuating lever  5  includes a pair of locating portions  51  pivotally received in the slots  302  of the locating blocks  301 , and an operation handle  52  perpendicularly bent from one of the locating portions  51  and located generally in alignment with the second beam  31 . The handle  52  can rotate relate to the frame  3  between an open position in which the handle  52  is substantially perpendicular to the frame  3 , and a closed position in which the handle  52  is substantially parallel to the frame  3 . The lever  5  further includes an offset pressing portion  511  between the locating portions  51 . Referring to FIG. 2, the pressing portion  511  is positioned onto the hook  411  of the pressing plate  4  to locate the hook  411  in the recess  306  of the frame  3 . 
     Referring to FIG. 3, in use, each locating portion  51  is located at the lowest portion  3020  of a corresponding slot  302 . The lever  5  is thus in an open position. In this position, the locating portion  51  only lightly contacts a base portion of an adjacent tongue portion  303 , and the tongue portion  303  does not exert any pressing force on the locating portion  51 . However, the locating portion  51  is liable to be subjected to a sudden unwanted external force, which may drive the locating portion  51  to slide away from the lowest portion  3020 . Under these circumstances, the lower surface  3032  of the tongue portion  303  resists the locating portion  51 , and generates a pressing force along a direction opposite to a direction of sliding of the locating portion  51  so as to push the locating portion  51  back to the lowest portion  3020 . FIG. 4 shows the locating portion  51  having been slid to the highest portion  3022  of the slot  302 . The lever  5  is thus in a closed position. In this position, the pressing portion  511  of the lever  5  has rotated to press the hook  411  of the pressing plate  4  and generate a downward pressing force toward the housing  2  for locating the housing  2 . Moreover, friction force between the pressing portion  511  and the hook  411  is large enough to overcome push-back force exerted by the tongue portions  303  on the locating portions  51 , thereby preventing the locating portions  51  from being pushed back to the lowest portions  3020  of the slots  302 . 
     FIGS. 5,  6  and  7  show a connector assembly  1 ′ in accordance with the alternative embodiment of the present invention. The connector assembly  1 ′ has substantially the same structure as the connector assembly  1  of the preferred embodiment, except for a structure and function of tongue portions  303 ′ of the connector assembly  1 ′. Referring to FIG. 6, a lower surface  3032 ′ of each tongue portion  303 ′ comprises two contiguous concave arcs joined by a projection  3034 ′. That is, the lower surface  3032 ′ comprises a lower arc and an upper arc. This feature enables a corresponding locating portion  51 ′ to be securely positioned at either a lowest portion  3020 ′ or a highest portion  3022 ′ of a slot  302 ′. That is, after the locating portion  51 ′ is slid to the highest portion  3022 ′ of the slot  302 ′, the projection  3034 ′, in cooperation with pushing force exerted from the upper arc, prevents the locating portion  51 ′ from sliding back from the highest portion  3022 ′. 
     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.