Abstract:
Deformation of a socket housing during connection of an IC package is prevented, and reliable electrical connections are secured in an IC socket assembly. The IC socket assembly is constituted by a plurality of electrical contacts; an insulative socket housing for holding the electrical contacts arranged in a matrix; a reinforcing plate having an opening at its center, through which the electrical contacts are exposed, for supporting the lower portion of the socket housing; a cover member, which is rotatably supported by the reinforcing plate, for cooperating with the reinforcing plate to sandwich and hold the IC package therebetween and to press the IC package against the electrical contacts; and reinforcing beams, which are supported by the reinforcing plate and provided across opposing edges of the opening, for supporting the socket housing.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to an IC socket assembly and more particularly to an IC socket assembly wherein a socket housing and an IC package placed atop the socket housing are sandwiched between a reinforcing plate provided below the socket housing and a cover member for pressing the IC package against the socket housing.  
       BACKGROUND  
       [0002]     A conventional IC socket assembly for a PGA (Pin Grid Array) package is disclosed in Japanese Unexamined Patent Publication No. 2002-313509 (FIG. 1, FIG. 11). This IC socket assembly comprises a base housing, which is constructed by molding plastic material over a metallic reinforcing plate having a square frame shape. In this PGA socket, a terminal mounting portion is positioned at the approximate center of the base housing. The metallic reinforcing plate reinforces the periphery of the terminal mounting portion. A cam driven sliding plate is provided on the base housing. An IC package is placed on the sliding plate. Lead pins of the IC package, engage with terminals, which are provided in the terminal mounting portion, by a horizontal sliding motion of the sliding plate, thereby establishing electrical connections between the lead pins and terminals.  
         [0003]     In the conventional IC socket assembly described above, the terminals apply a force to the base housing during engagement of the lead pins and the terminals. This force works to deform the base housing. The base housing is reinforced by the square frame shaped metallic reinforcing plate to counter this force. However, the base housing is reinforced only at the periphery thereof. An opening is formed at the terminal mounting portion, where the terminals are provided. Thus the terminal mounting portion, to which force is applied by the terminals, is not reinforced. Accordingly, there is a possibility that deformation of the base housing will occur at the terminal mounting portion.  
         [0004]     In another known IC socket assembly, a cover member presses, from above, on an IC package placed atop a socket housing to connect lead pins of the IC package to electrical contacts of the socket housing. In this IC Socket, the force from above is applied to the socket housing via the electrical contacts, and there is a possibility that the housing may be deformed and bend. Generally, IC sockets are mounted on printed circuit boards by soldering. However, excessive force is applied in a direction that acts to separate the socket housing from the circuit board at solder connections, particularly of the electrical contacts positioned at the peripheral portions, due to warping or bowing of the socket housing. In addition, the electrical contacts at the central portion separate from the IC package, and contact pressures as set by design cannot be obtained. Accordingly, it is difficult to realize highly reliable electrical connections in a state in which this force is applied.  
         [0005]     However, the electrical contacts mounted in this type of IC socket assembly are arranged in a matrix. Therefore, it is difficult to prevent deformation of the socket housing by reinforcing the socket housing at a terminal mounting portion.  
       SUMMARY  
       [0006]     According to an exemplary embodiment of the present invention, an IC socket assembly is providing that comprises: 
        a plurality of electrical contacts;     an insulative socket housing for holding the electrical contacts arranged in a matrix;     a frame-shaped reinforcing plate for supporting the lower portion of the socket housing, having an opening at its central portion through which the electrical contacts are exposed; and     a cover member, which is pivotally supported by the reinforcing plate, for sandwiching an IC package between the cover and the socket housing and for pressing the IC package against the electrical contacts; wherein reinforcing beams for supporting the socket housing are provided across opposing edges of the opening, supported by the reinforcing plate. A plurality of reinforcing beams may be provided.       
 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a plan view of an IC socket assembly according to an exemplary embodiment of the present invention.  
         [0012]      FIG. 2  is a front view of the IC socket assembly of  FIG. 1 .  
         [0013]      FIG. 3  is a vertical sectional view of the IC socket assembly of  FIG. 1 , taken along line III-III of  FIG. 1 .  
         [0014]      FIG. 4  is a bottom view of the IC socket assembly of  FIG. 1 .  
         [0015]      FIG. 5  is a vertical sectional view of the IC socket assembly of  FIGS. 1-4 , taken along line V-V of  FIG. 4 .  
         [0016]      FIG. 6  is a sectional view of the IC socket assembly of  FIGS. 1-5 , taken along line VI-VI of  FIG. 1 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]     Hereinafter, an IC socket assembly (hereinafter, simply referred to as “assembly”) according to a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.  
         [0018]     First, the schematic construction of the assembly  1  will be described with reference to  FIG. 1 . The assembly  1  comprises an insulative socket housing  2  (hereinafter, simply referred to as “housing”); a cover member  8 ; a metallic reinforcing plate  10  (hereinafter simply referred to as “reinforcing plate”); and a lever  12 . In a exemplary embodiment, the housing  2  is molded from resin. The cover member  8  is pivotally mounted to the housing  2  at a first end  4  thereof, and has a substantially rectangular opening  68 . The reinforcing plate  10  is mounted on the bottom surface of the housing  2  (refer to  FIG. 4 ). The lever  12  is axially supported at a second end  6  of the housing  2 , and has a function of locking (engaging) the cover member  8 . A great number of contacts  90  are provided in the housing  2 . Note that an IC package  200 , which is to be placed on the housing  2 , is indicated by broken lines in  FIG. 5 .  
         [0019]     Next, the housing  2  will be described in detail. The housing  2  is formed as a rectangular plate having a rectangular opening  22  at its center. An upwardly extending peripheral wall  24  (refer to  FIG. 5  and  FIG. 6 ) is erected about its upper periphery, to constitute an IC package housing portion  26  (refer to  FIG. 5  and  FIG. 6 ) which is open in an upward direction. A substantially rectangular lower mounting portion  28  is integrally formed with the housing  2 , at a position corresponding to the IC package housing portion  26 . The opening  22  is provided to house electronic components such as condensers (not shown) of the IC package  200 , which is placed in the IC package housing portion  26 , and of a circuit board  150  (refer to  FIG. 5 ).  
         [0020]     A great number of contact apertures  32  are formed in a matrix in the bottom surface of the IC package housing portion  26 , (i.e., an IC package mounting surface  30  shown in  FIG. 5 ), extending through the mounting portion  28 . The contacts  90  are press fit and fixed within the contact apertures  32 . When the contacts  90  are completely mounted within the contact apertures  32 , solder balls  90   b , which are to be soldered to the circuit board  150 , are exposed at a lower surface  38  of the housing  2 . At the same time, elastic contact pieces  90   a , for contacting contacts (not shown) of the IC package  200  protrude through the IC package mounting surface  30 .  
         [0021]     As most clearly illustrated in  FIG. 4 , the contact apertures  32 , which are arranged in a matrix, are divided into three groups by border regions  34 . The border regions  34  extend linearly from the first end  4  of the assembly  1  to the second end  6 , via two edges of the opening  22 . Grooves  36  for mounting reinforcing beams  72 , to be described later, are formed in the border regions  34  from the vicinity of a front end  2   a  of the housing  2  to the vicinity of the opposing rear end  2   b  thereof (refer to  FIG. 5 ).  
         [0022]     The reinforcing beams  72 , which are placed in the grooves  36  of the housing  2 , are, in an exemplary embodiment, constituted by planar metallic members having thicknesses, that is, widths, corresponding to the depths of the grooves  36 , as illustrated in  FIG. 5  and  FIG. 6 . Downwardly facing step portions  72   a , to be seated on the edges of an opening  40  of the reinforcing plate  10 , are formed at both ends of the reinforcing beams  72 . The reinforcing beams  72  are wide (as shown in  FIG. 5 ), whereas the thickness of the reinforcing beams  72  in the direction perpendicular to the width is small (as shown in  FIG. 6 ). Therefore, the border regions  34  can be made narrow. Accordingly, the area of the circuit board occupied by the reinforcing beams  72  can be minimized, as well as minimizing the effect that the provision of the reinforcing beams  72  causes on the number of contacts  90 . The function of the reinforcing beams  72  will be described in detail later.  
         [0023]     Next, the reinforcing plate  10  that supports the housing  2  from below will be described in detail. As most clearly illustrated in  FIG. 4 , the reinforcing plate  10  of the illustrated exemplary embodiment is formed by punching and bending a single metal plate into a substantially rectangular frame shape. The aforementioned opening  40 , which is of a shape complementary to the mounting portion  28 , is formed in the approximate center of the reinforcing plate  10 . The mounting portion  28  is positioned within the opening  40  and protrudes downward from the reinforcing plate  10  (refer to  FIG. 6 ).  
         [0024]     The four sides of the reinforcing plate  10  are bent upward to form a front wall  42 , a rear wall  44 , and side walls  46 ,  48 . Holding pieces  50  and  52  are formed by bending the top of the front wall  42  inward. The holding pieces  50  and  52  are separated from each other in the lengthwise direction of the front wall  42 , and serve to prevent rotating shafts  54  of the lever  12 , to be described later, from being pulled out. Front ends  46   a  and  48   a  of the side walls  46  and  48  are positioned below the rotating shafts  54  of the lever  12 , and cooperate with the holding pieces  50  and  52  to axially support the rotating shafts  54  in a rotatable manner.  
         [0025]     Two rectangular openings  56  are formed in the rear wall  44  of the reinforcing plate  10 , separated in the lengthwise direction of the rear wall  44 . The openings  56  serve to pivotally support the cover member  8 . In an exemplary embodiment, the housing  2  is fixed to the reinforcing plate  10  by heat welding four protrusions  58  (shown in  FIG. 4 ) erected on the housing  2  to the opening  40  of the reinforcing plate  10 . An engaging protrusion  14  that protrudes toward the lateral exterior, for fixing the lever  12 , is formed on the side wall  46  of the reinforcing plate  10 .  
         [0026]     Next, the lever  12  for locking and releasing the cover member  8 , will be described. In an exemplary embodiment, the lever  12  is formed by bending a single metallic wire, and comprises: two separate rotating shafts  54 , which are supported by the holding pieces  50  and  52 ; a crank portion, that is, a locking portion  62 , which is offset from the rotating shafts  50  and  52  and positioned therebetween; a lever arm or operating rod  64 ; and an operating portion  66 , for rotating the rotating shafts  54 . The operating rod  64  is bent perpendicular to the rotating shafts  54  in substantially the same direction that the locking portion  62  is offset therefrom. The operating portion  66  is formed by bending the operating rod  64  in a U shape.  
         [0027]     Next, the cover member  8  will be described. Note that in the description, the portion of the cover member  8  positioned at the first end  4  of the assembly  1  will be referred to as the rear, and the portion of the cover member  8  positioned at the second end  6  will be referred to as the front. In an exemplary embodiment, the cover member  8  is formed by punching and bending a single metal plate into a substantially rectangular shape. A locking piece  70 , which is to be pressed and held by the locking portion  62 , is formed at the center of the front portion of the cover member  8 . Support pieces  60 , to be inserted into the aforementioned openings  56  thereby engaging the reinforcing plate  10 , are formed at both sides of the rear portion of the cover member  8 . The support pieces  60  are curved in an arcuate manner from below to above (refer to  FIG. 5 ). The cover member  8  pivots about the engagement between the support pieces  60  and the openings  56 , and is prevented from being disengaged. Note that the side of the cover member  8  at which the support pieces  60  are formed is referred to as the “axial support side”, and the side of the cover member  8  at which the locking piece  70  is formed is referred to as the “engagement side”.  
         [0028]     A substantially rectangular opening  68 , at which the IC package  200  is positioned, is formed in the center of the cover member  8 . Note that as can be seen in  FIG. 3  and  FIG. 5 , that the peripheral edges of the opening  68  are slightly curved downward. The reason for this curvature is to facilitate control of the load exerted on the IC package  200 , when it is pressed against the assembly  1  by the cover member  8 . In addition, cutouts  69  (shown in  FIG. 1 ) are formed toward the side of the first end  4 , to eliminate interference with a flange  202  (shown in  FIG. 5 ) of the IC package  200  when the cover member  8  is closed, thereby ensuring engagement between the locking portion  62  and the locking piece  70 .  
         [0029]     Next, a case in which the assembly  1  constructed as described above is utilized will be described. First, the lever  12  illustrated in  FIG. 1  is disengaged from the engaging protrusion  14  and rotated 90 degrees in the direction toward the viewer of  FIG. 1 . Thereby, the engagement between the locking portion  62  and the cover member  8  is disengaged and pivoting of the cover member  8  about the axial support is enabled. Then, the IC package  200  is placed on the housing  2  as illustrated in  FIG. 5 , the cover member  8  is closed, and the lever  12  is rotated so that the locking portion  62  presses and fixes the locking piece  70 . At this time, the upper surface of the flange  202  of the IC package  200  is pressed by the downwardly curved surface of the cover member  8 .  
         [0030]     The pressure exerted by the cover member  8  is the force that presses the IC package  200  against the contacts  90  of the housing  2 . This force also acts to press the housing  2  downward and to deform the housing  2  via the contacts  90 . However, the housing  2  is supported by the reinforcing beams  72 , which in turn are supported by the reinforcing plate  10 . Therefore, downward deformation of the housing  2  is prevented. The periphery of the housing  2  is supported by the reinforcing plate  10 , therefore the housing  2  is extremely effectively supported from below by the cooperation of the reinforcing plate  10  and the reinforcing beams  72 . Accordingly, the possibility of problems, such as damage to the solder connecting portions between the contacts  90  in the peripheral portions and the circuit board  150 , is reduced. At the same time, separation of the contacts  90  in the central portion from the IC package  200  is also prevented.  
         [0031]     The present invention has been described in detail above. However, the present invention is not limited to the above embodiment. Rather, various changes and modifications are possible within the scope of the present invention. For example, three or more reinforcing beams  72  may be provided instead of two.  
         [0032]     In addition, the above embodiment describes a case in which an opening  22  is provided in the central portion of the housing  2 . However, a configuration may be considered in which there is no opening  22 . In this case, contacts are arranged in a matrix at the portion of the housing corresponding to the opening  22 . Therefore, it is possible to provide a single reinforcing beam at the center of the mounting portion.