Patent Document

BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an electrical connector, and more particularly to a socket connector for electrically interconnection with a pin grid array (PGA) package to a printed circuit board (PCB). 
   2. Description of Prior Arts 
   Integrated circuits (ICs) are becoming smaller, more complex, and more prevalent. It is common for a modern electronic appliance, such as a computer, to have several IC components attached to a circuit board. Each IC is generally delivered as an enclosed package with a pin grid array (PGA) interface. The PGA interface is a set of electrically conductive pins arranged in a pattern, where each pin is an electrical connection to the functional portion of the IC. In order to install the IC in an electronic appliance, the pins must be electrically connected to appliance&#39;s main circuit board. It is thus desirable for there to be a simple mechanism that permits the IC to be quickly and easily attached to the circuit board, while minimizing the risk of damage. 
   One device that permits a simple, fast connection between an IC and a circuit board is a Zero Insertion Force (ZIF) socket assembly. A ZIF socket assembly is a device having set of contacts in electrical connection with the circuit board, where the contacts are disposed in a set of sockets. The device is arranged such that the pins of the IC can be inserted into the sockets without touching the contacts so that the pins do not encounter frictional resistance as they are inserted. Subsequent to the insertion of the pins, the device brings the pins and contacts into electrical connection, such that electrical impulses can flow freely between the pins and the circuit board by way of the contacts. 
   A number of ZIF socket devices have been proposed. A typical ZIF socket assembly may utilize a plastic socket cover that is slidably movable on a plastic socket base between an open position and a closed position. Generally, an actuating mechanism is used to drive the cover and the base between the open and closed positions. One type of actuating mechanism according to the prior art is an eccentric cam shaft which is basically in the form of a screw member which is operated by an appropriate tool, such as a screwdriver. The eccentric cam shaft has an eccentric portion engageable with the socket cover and moving the socket cover relative to the socket base. 
   Generally, referring to  FIG. 1 , the ZIF socket assembly further includes a plate  27  that is retained in a recessed area  225  on a bottom of the socket base  22 , wherein the plate  27  is formed of metal or another suitably hard materials to absorb forces created by the eccentric cam shaft, thereby protecting plastic area of the socket base  22  from cracking and giving the ZIF socket assembly a long-life span. More specifically, for some demands, the plate  27  has a rough surface facing the bottom of the recessed area and a slippery surface opposite to the rough surface facing exterior to be cooperated with other subassembly (not shown). However, since the conventional plate  27  is geometrical symmetry, the ZIF socket assembly is suffered from several drawbacks, and particularly, problem will be encountered in attempting to assemble the plate  27  to the recessed area  225  of the socket base  22 . During the course of assembling, the rough surface of plate  27  is inclined to mistakenly face exterior without notice so as to wear and tear the subassembly, resulting in a shorten life of the subassembly. 
   In light of the problem, an improved socket connector is desired to overcome the drawback of the prior arts. 
   SUMMARY OF THE INVENTION 
   Accordingly, the main object of the present invention is to provide a socket connector having keying means which is provided between a base plate and a recessed area on a socket base for preventing mismating. 
   To fulfill the above-mentioned object, a socket connector according to the present invention comprises a socket base, a socket cover slidable mounted on the socket base, a base plate received in a recessed area defined in the socket base, and an eccentric cam member rotatable engaging with the socket cover, the socket base and the base plate so as to actuate the socket cover to move with respective to the socket base between an open position and a closed position. Keying means is provided between the base plate and the recessed area so as to prevent the base plate from mismating with the base. 
   Other objects, advantages and novel features of the invention will become more apparent from the following detailed description of the present embodiment when taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The organization and manner of the structure and operation of the invention, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawings, wherein like reference numerals identify like elements in which: 
       FIG. 1  is a partially exploded, bottom view showing a conventional base plate and a corresponding recessed area on a bottom of a socket base; 
       FIG. 2  is an exploded, perspective view of a socket connector in accordance with the present invention; 
       FIG. 3  is a partially exploded, perspective view showing a base plate and a socket base in accordance with the present invention; 
       FIG. 4  is an assembled, perspective view of the socket connector in accordance with the present invention; and 
       FIG. 5  is an assembled, bottom plan view of the base plate and the socket base of  FIG. 3 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Reference will now be made to the drawings to describe the present invention in detail. 
     FIG. 2  illustrates an exploded view of a socket connector  100  in accordance with a preferred embodiment of the present invention. The socket connector comprises an insulated socket base  12 , an insulated socket cover  13  slidably mounted on the socket base  12 , and a metallic eccentric cam member  15  rotationally embedded in the socket base  12  and the socket cover  13  for actuating the socket cover  132  to slide along the socket base  12  between an open position and a closed position. 
   The socket base  12  is generally in shape of a rectangular, and comprises an insulative base housing  120  and a base extension  121  extending from one side of the base housing  120 . The base housing  120  defines a plurality of base passages  1201  extending vertically therethrough to receiving a plurality of contacts (not shown). The base extension  121  forms a pair of spaced standoffs  122  extending upwardly from opposite sides of upper face thereof, and accordingly defines a receiving space  123  therebetween, wherein each of the standoffs  122  defines a small rectangular depression  1220  communicating with the receiving space  123 . Furthermore, referring to  FIG. 2  in conjunction with  FIG. 3 , the base extension  121  defines a downwardly opening recessed area  125  in the middle of bottom face and a roundish base hole  1232  extending through bottom of the recessed area  125  to communicate with the receiving space  123 . The recessed area  125  is generally in H-shaped that receives a base plate  17 . A U-shaped notch  1252  is cut into the base  12  from one elongated side of the recessed area  125 , wherein a centerline of the notch  1252  is offset to that of the recessed area  125 . 
   Referring to  FIGS. 3–5 , the base plate  17  is formed of metal or another suitably hard materials. For some special demands, the base plate  17  has a rough upper surface facing the bottom of the recessed area  125  and a lower slippery surface opposite to the rough upper surface. In the preferred embodiment of the present invention, the base plate  17  is generally H-shaped configuration corresponding to the shape of the recessed area  125 , and defines a pair of cutouts  174  cut from opposite lateral sides thereof and a roundish base plate hole  170  going halves the cutouts  174 . Furthermore, the base plate  17  has a rectangular projection  172  projecting outwardly from one elongated side thereof to be received in the notch  1252  of the base  12 , wherein a centerline I of the projection  172  is offset to a centerline II the base plate  17  and in align with that of the notch  1252  as best shown in  FIG. 5 . 
   Returning to  FIG. 2 , the socket cover  13  has a shape corresponding to that of the socket base  12 , and comprises an insulative cover housing  130  and a cover extension  132  extending from one side of the cover housing  130  to be received in the receiving space  123  of the base  12 . The cover housing  130  defines a plurality of cover passages  1301  in alignment with the base passages  1201  of the base housing  120  for receiving a plurality of pins of pin grid array (PGA) package. The cover extension  132  defines a rectangular cover hole  1320  in middle thereof and a pair of indentions  134  nearest the cover housing  130  and spaced by the cover hole  1320 . 
   A T-shaped cover plate  16  is provided above the cover extension  132  of the socket cover  13 . The cover plate  16  is a planar plate of metal or another suitably hard materials and defines a rectangular cover plate hole  1602  in alignment with the cover hole  1320  and a pair of embossments  1604  extending downwardly from bottom face thereof for being fitted into the indentions  134  of the cover  13 . 
   The eccentric cam member  15  comprises an upper portion  150 , a middle portion  152  and a lower portion  154 , wherein the upper portion  150 , the middle portion  152  and the lower portion  154  are generally in shape of cylindrical, but have taper-off diameters. The upper portion  150  defines an elongated groove  1501  recessed in upper face thereof for receiving a blade-like external tool (not shown) such as a screwdriver and forms a lateral protrusion  1502  outwardly protruding beyond a part of periphery thereof. The middle portion  152  is overlapped by the upper portion  150  along perimeter thereof. The lower portion  154  is formed beneath the middle portion  152  and has a riveting end  1540  (shown in  FIG. 4 ) at a lower end thereof. It is to be noted that a rotational axis of the middle portion  152  is offset from a rotational axis of the upper portion  150  (shown in  FIG. 5 ), and elaboration will be given hereinafter. 
   A cam plate  14  is provided as a planar plate of metal or another suitably hard materials and has an elongated main body  140  and a pair of ears  142  extending outwardly from opposite lateral sides of the main body  140 . The main body  140  defines a roundish cam plate hole  1402  in a middle thereof and forms a pair of cam stoppers  1404  symmetrically on opposite sides of the cam plate hole  1402  along a horizontal direction. The cam stoppers  1404  are apt to prevent the eccentric cam member  15  from been over rotated between the open and the closed positions when the socket connector  100  is fully assembled. 
   In addition, the socket connector  100  comprises a washer  18  also made of metal or another suitably hard materials. The washer  18  is a round in shape and defines an aperture  180  in middle thereof for receiving the riveting end  1540  of the eccentric cam member  15 . 
   In assembly, the base plate  17  is fitted into the recessed area  125  of the socket base  12  such that the projection  172  is received in the notch  1252 . Successively, the socket cover  13  together with the cover plate  16  is assembled onto the socket base  12 , and the cam plate  14  is assembled onto the socket base  12  and above the cover plate  16 . The cover extension  132  of the cover  13 , the cover plate  16  attached to the cover extension  132 , and the cam plate  14 , are disposed in the receiving space  123  of the socket base  12 . The ears  142  of the cam plate  14  engage with the depressions  1220  of the standoffs  122  for securing the cam plate  14  in position. At this time, the base plate hole  170 , the base hole  1232 , the cover hole  1320 , the cover plate hole  1602  and the cam plate hole  1402 , respectively, are all aligned and commonly receive the eccentric cam member  15 . Finally, the washer  18  is assembled to the riveting end  1540  of the eccentric cam member  15 . In such a way, the eccentric cam member  15  is rotatably secured to the socket base  12  and the socket cover  13  and the socket connector  100  is fully assembled. 
   In operation, after the PGA package is loaded on the socket cover  13 , the eccentric cam member  15  is rotated by the external tool until the lateral protrusion  150  engages with one of cam stoppers  1404 . During the process, since the rotational axis of the middle portion  152  is offset from the rotational axis of the upper portion  150 , the middle portion  152  of the eccentric cam member  15  abuts against inner segments of the cover plate hole  1602  and the cover hole  1320  to apply forces against the socket cover  13 , synchronously, the socket cover  13  slides along the base  12  in a closed position, wherein the pins of the PGA package electrically connect with corresponding contacts retained in the socket base  12 . To open the connection between the pins and the contacts, the eccentric cam member  15  is rotated in an opposite direction from one of the cam stoppers  1404 , to the other cam stoppers  1404 . For the same reason, the socket cover  13  slides along the socket base  12  in an open position, thereby allowing the PGA chip to be removed from the socket connector  100 . 
   During the operation, since the cam plate  14 , the cover plate  16 , the base plate  17  and the washer  18  are made of metal or another suitably hard materials, plastic area of the base extension  121  and the cover extension  132  abutted against by the eccentric cam member  15  is protected, thereby giving the socket connector  100  a long-life span and enhancing the retention between the socket base  12  and the socket cover  13 . 
   In the preferred embodiment, keying means is provided between the base plate  17  and the recessed area  125  of the socket base  12  so as to prevent the base plate  17  from mismating with the socket base  12 . The keying means includes the projection  172  projecting from one elongated side of the base plate  17  and the notch  1252  notched into the socket base  12  from the recessed area  125  for receiving the projection  172 , wherein the centerline I of the projection  172  is offset to the centerline II of the base plate  17 . 
   In one alternative embodiment, the keying means may be located in different positions between the base plate  17  and the recessed area  125 , for example, the projection  172  projecting from one lateral side of the base plate and the notch  1252  notched from corresponding position of the recessed area  125 , or plurality of projections  172  suited and asymmetric projecting from base plate  17  and plurality of notches notched from corresponding positions of the recessed area  125 . 
   In another alternative embodiment, the keying means is also provided between the base plate  17  and the recessed area  125 , but employs an opposite co-work relationship, for example, the projection  172  projecting from one inner wall of the recessed area  125  and the notch  1252  notched into corresponding position of the base plate  17  for receiving the projection  172 , so do the plurality of projections  172  and the corresponding notches  1252 . 
   In further alternative embodiment, the base plate  17  and the corresponding recessed area  125  may have any variety of different shapes and sizes, such as circular, rectangular, star-shaped, triangular, hexagonal, or any other geometric or non-symmetric shape. 
   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.

Technology Category: h