Patent Publication Number: US-6702588-B1

Title: Electrical connector assembly with snap-fit base and frame

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electrical connector assembly for electrically connecting an electronic package such as a central processing unit (CPU) with a circuit substrate such as a printed circuit board (PCB), and particularly to a land grid array (LGA) connector assembly having a base and a frame readily joined together. 
     2. Description of the Prior Art 
     Electrical connector assemblies are widely used for electrically connecting land grid array (LGA) central processing units (CPUs) with printed circuit boards (PCBs). This kind of connector assembly is described in “Nonlinear Analysis Helps Design LGA Connectors”, which is obtained from the web journal “Connector Specifier” (February, 2001). A similar electrical connector assembly is disclosed in U.S. Pat. No. 5,344,334. 
     Generally, each such conventional electrical connector assembly is mounted on a PCB that defines four bores. The electrical connector assembly comprises a base receiving a plurality of electrical contacts therein, and a frame assembled on the base. The frame defines an opening in a middle thereof, and four screw holes at respective corners thereof. The base defines a plurality of passageways receiving the contacts therein, and four holes corresponding to the screw holes of the frame. In assembly, the base is attached on the PCB, with the holes of the base above the corresponding bores of the PCB. The frame is attached on the base, with the screw holes above the corresponding holes of the base. Four bolts are extended through respective bores of the PCB and respective holes of the base to engage in respective screw holes of the frame, thereby assembling the electrical connector assembly with the PCB. 
     However, it takes an unduly long time to screw the bolts when assembling the electrical connector assembly with the PCB. This retards the efficiency of assembly, which is particularly significant in mass production facilities. In addition, the base and the frame are at all times separate parts prior to their assembly on the PCB. This increases the difficulty of transporting and handling the base and the frame. 
     In view of the above, a new LGA connector assembly that overcomes the above-mentioned disadvantages is desired. 
     SUMMARY OF THE INVENTION 
     Accordingly, a main object of the present invention is to provide an electrical connector assembly for electrically connecting a CPU and a PCB, wherein the connector assembly can be readily assembled on the PCB. 
     Another object of the present invention is to provide an electrical connector assembly having a base and a frame that can be assembled together prior to mounting of the electrical connector assembly on a PCB. 
     To achieve the above-mentioned objects, an electrical connector assembly in accordance with a preferred embodiment of the present invention is mounted on a PCB that defines two bores diagonally opposite from each other. The electrical connector assembly comprises a base, a plurality of electrical contacts received in the base, and a frame assembled on the base. The frame defines an opening in a middle thereof, two fixing holes at diagonally opposite corners thereof, and two semi-circular orientation holes at two opposite sides thereof. The fixing hole is surrounded by a circumferential step thereat. The frame includes a planar portion having a top surface and a bottom surface. A pair of orientation projection extends perpendicularly from the top surface of the planar portion, for interferentially engaging in the orientation holes of the frame. A pair of fixing posts extends perpendicularly from the top surface of the planar portion, for snappingly engaging in the fixing holes of the frame to firmly mount the frame on the base. A pair of protrusions is located below respective orientation projections, with the protrusions depending from the bottom surface of planar portion. The protrusions interferentially engage in the bores of the PCB to firmly mount the electrical connector assembly on 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, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a simplified, exploded isometric view of an electrical connector assembly in accordance with the preferred embodiment of the present invention, together with an LGA CPU and a PCB; 
     FIG. 2 is an enlarged view of a circled portion II of FIG. 1; 
     FIG. 3 is an enlarged view of a circled portion III of FIG. 1; 
     FIG. 4 is a simplified, isometric view of a base of the electrical connector assembly of FIG. 1, but showing the base inverted; 
     FIG. 5 is an enlarged view of a circled portion V of FIG. 4; 
     FIG. 6 is an assembled view of the electrical connector assembly and the PCB of FIG. 1, partly cut away; and 
     FIG. 7 is an enlarged view of a circled portion VII of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION 
     Reference will now be made to the drawings to described the present invention in detail. 
     Referring to FIG. 1, an electrical connector assembly  1  of the present invention is used for electrically connecting a land grid array (LGA) central processing unit (CPU)  3  with a printed circuit board (PCB)  2 . The PCB  2  defines two bores  21 , which are generally diagonally opposite from each other. The electrical connector assembly  1  comprises a base  11 , a plurality of electrical contacts (not shown) received in the base  11 , and a frame  12  assembled on the base  11 . 
     Also referring to FIGS. 2,  3 ,  4  and  5 , the base  11  comprises a planar portion  111 , and a pair of forked fixing posts  116 , a pair of orientation projections  119  and a pair of protrusions  117  respectively extending from the planar portion  111 . The planar portion  111  has a top surface  115 , and a bottom surface  114  opposite to the top surface  115 . The planar portion  111  defines a plurality of passageways  113  extending therethrough. The passageways  113  are arranged in a rectangular array for respectively receiving the contacts therein. The fixing posts  116  are formed at diagonally opposite corners of the planar portion  111 . Each fixing post  116  comprises a body portion  1161  extending perpendicularly from a respective corner of the planar portion  111 , a cap  1162  on a top of the body portion  1161 , and a vertical slot  1163 . The slot  1163  bifurcates the cap  1162  and the body portion  1161 , thus providing the fixing post  116  with elasticity in transverse directions during assembly. The orientation projections  119  are formed at two opposite sides of the planar portion  111 . Each orientation projection  119  extends perpendicularly upwardly from the top surface  115 . Each orientation projection  119  has a generally semi-circular horizontal cross-section, and comprises a plurality of spaced, vertical first ribs  1190  around a periphery thereof. Each protrusion  117  is generally cylindrical with a frustum-shaped free end, and comprises a plurality of vertical second ribs  1170  around a periphery thereof. The protrusions  117  are located below respective orientation projections  119 , with the protrusions  117  depending from the bottom surface  114 . 
     The frame  12  is substantially rectangular, with four beams  120  defining an opening  121  therebetween for receiving the CPU  3  therein. Each of two opposite of the beams  120  defines a semi-circular orientation hole  122  therethrough, the orientation holes  122  corresponding to the orientation projections  119  of the base  11 . The frame  12  defines two fixing holes  123  at diagonally opposite corners thereof, the fixing holes  123  corresponding to the fixing posts  116  of the base  11 . Each fixing hole  123  is surrounded by a circumferential step (not shown) thereat. 
     Referring to FIGS. 6 and 7, in assembly of the base  11  and the frame  12 , the frame  12  is positioned above the base  11 , with the orientation projections  119  beneath the corresponding orientation holes  122 , and the fixing posts  116  beneath the corresponding fixing holes  123 . Then the frame  12  is pushed down onto the base  11 , and the fixing posts  116  elastically deform. When the fixing posts  116  are fully received in the fixing holes  123  and the orientation projections  119  are fully received within the orientation holes  122 , the fixing posts  116  elastically rebound to their original shapes. The caps  1162  of the fixing posts  116  abut against corresponding steps of the fixing holes  123 . The first ribs  1190  interferentially engage the orientation projections  119  in the orientation holes  122 . The frame  12  is thereby firmly mounted on the base  11 . 
     In assembly of the electrical connector assembly  1  and the PCB  2 , the electrical connector assembly  1  is positioned above the PCB  2 , with the protrusions  117  of the base  11  above the corresponding bores  21  of the PCB  2 . The electrical connector assembly  1  is pushed down onto the PCB  2 . The second ribs  1170  interferentially engage the protrusions  117  in the bores  21 . The electrical connector assembly  1  is thereby firmly mounted on and electrically connected with the PCB  2 . When the CPU  3  is mounted in the opening  121  of the frame  12 , the CPU  3  is firmly engaged on the planar portion  111  of the base  11  by retention means such as a clip assembly (not shown). The CPU  3  is thus electrically connected with the PCB  2 . 
     While a preferred embodiment in accordance with the present invention has been shown and described, equivalent modifications and changes known to persons skilled in the art according to the spirit of the present invention are considered within the scope of the present invention as defined in the appended claims.