Patent Document

BACKGROUND OF THE INVENTION 
   The present invention relates generally to electrical sockets, and, more particularly, to electrical sockets that receive reinforced corners. 
   In some types of electronic packaging, electrical sockets are provided that are surface mounted to a printed circuit board. For example, land grid array (“LGA”) and ball grid array (“BGA”) packaging include socket structures surface mounted to printed circuit boards including a matrix of corresponding surface mounted flat pad structures upon each of which is deposited a small quantity of solder. To mount the socket structure to the circuit board, the socket is typically placed on an appropriate side of the circuit board, using a high accuracy “pick and place” machine, in a manner such that the solder lead portions of the socket contact a number of flat, surface mounted solder pads on the board. Once the socket is located on the board, the board is heated, causing the solder to melt, thereby fusing the corresponding surfaces together and yielding a strong mechanical and electrical connection when cooled. 
   Even slight nonplanarities in either or both of the circuit board and surface mounted electronic packages tend to compromise the electrical connections of the electronic package to the board. Consequently, nonplanarities of the board or the electronic package tend to significantly increase the probability of having to rework a significant portion of the fabricated circuit board/electronic package assemblies, thereby undesirably increasing assembly and reducing yield. 
   As the data transmission rates of modern electronic devices increase, the size of the electronic package to accommodate an increased number of signals is also increasing. For example, in at least one application, sockets are required that approach 74 mm in length. An increased size of the packages, however, tends to result in warping of the plastic sockets used in the packages as they are surface mounted to the board. Specifically, heat from the solder reflow process creates residual stress in the plastic socket as the socket cools, thereby causing the socket to warp and become nonplanar with respect to the circuit board. Distortion and deformation of the socket is an undesirable and unwelcome aspect of the surface mount electronic package assembly. 
   BRIEF DESCRIPTION OF THE INVENTION 
   A cover for an electrical socket is provided in accordance with one aspect of the present invention. The cover comprises multiple walls joined with one another and configured to overlay an electrical socket. A latch element is provided on at least one of the walls to securely retain the walls against the electrical socket. A rigid member is secured to the walls and retains the walls in a predefined relation with respect to one another. 
   Optionally, the said walls of the cover surround an opening that extends through the socket, and the rigid member spans the opening. In a further option, the rigid member includes a heat resistant plate rigidly mounted to the walls. 
   In another option, the walls of the cover include lower edges aligned in a common plane, and the lower edges are configured to abut against and retain the electrical socket in a common plane. In a further option, the walls include upper edges that abut against the rigid member which maintain the walls in a common planar relation with one another. In still another option, the walls include brackets that slidably receive the rigid member. 
   In accordance with another aspect of the present invention, the cover is provided with a latch beam that is pivotally mounted to one of the walls. The latch beam has a length oriented to extend along a length of one of the walls. The latch beam is configured to securely retain the electrical socket to the cover. 
   In accordance with still another aspect of the present invention, an electronic package is provided. The package comprises an electrical socket and a cover with multiple walls joined with one another and configured to overlay the electrical socket. A latch element is provided on at least one of the walls to securely retain the walls against the electrical socket. A rigid member is secured to the walls and retaining the walls in a predefined relation with respect to one another. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is perspective view of an exemplary electronic package assembly formed in accordance with an embodiment of the present invention. 
       FIG. 2  is a top plan view of a cover for the socket assembly shown in  FIG. 1  formed in accordance with an embodiment of the present invention. 
       FIG. 3  is an end elevational view of the cover shown in  FIG. 2  formed in accordance with an embodiment of the present invention. 
       FIG. 4  is an exploded perspective view of a reinforced cover assembly for the package shown in  FIG. 1  formed in accordance with an embodiment of the present invention 
       FIG. 5  is a top plan view of the package shown in  FIG. 1  with the cover assembly in a latched position. 
       FIG. 6  is a magnified view of a portion of the package shown in FIG.  5 . 
       FIG. 7  is a top plan view of the package shown in  FIG. 1  in an unlatched position. 
       FIG. 8  is a perspective view of another embodiment of an electronic package. 
       FIG. 9  is a partial cross sectional view of a portion of the socket and frame shown in FIG.  8 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is a perspective view of an exemplary electronic package  100  including a socket  102  and a cover assembly  104  attached to the socket  102 . As explained in detail below, cover assembly  104  overlays socket  102  and prevents socket  102  from warping such as during solder reflow processes in surface mount installations and such as in ball grid array (“BGA”) packaging. Package  100  is particularly suited for larger socket openings, such as for, example, a distributed power delivery system for an electronic device, although it is understood that the benefits of the invention and/or disclosed embodiments may be used in other applications. For example, while package  100  has been found to be advantageous for BGA packaging, it is recognized that package  100  may also be used in land grid array (“LGA”) packaging. The embodiments described hereinbelow are therefore set forth for purposes of illustration rather than limitation, and the invention is not intended to be limited to any particular socket configuration or to sockets for any particular end application. 
   Socket  102 , as further described below, is generally rectangular in shape in an exemplary embodiment and includes four sides  106  extending substantially perpendicular to one another and joined at respective ends thereof. Each side  106  of socket  102  includes a pair of projections or tabs  108 , sometimes referred to as fences, extending upwardly therefrom for secure engagement with cover assembly  104 . Socket  102  further includes a number of openings therein for receiving power and/or signal contacts of a mating electronic card interposer (not shown). In an illustrative embodiment, socket  102  is fabricated from known materials, including but not limited to injection molded plastic, and is configured for surface mounting to a printed circuit board (not shown). In other words, a bottom surface of socket  102  is substantially flat and coplanar to form a secure mechanical and electrical connection when surface mounted to the printed circuit board. While a generally rectangular socket configuration is illustrated, it is appreciated that other socket shapes having a greater or fewer number of sides may be employed. It is further recognized that a greater or fewer number of projections or tabs  108  may be employed. 
   As illustrated in  FIG. 1 , cover assembly  104  is generally complementary in shape to socket  102  and is configured to be hingedly attached to socket  102  through projections  108 . Upstanding side walls extend about the remaining sides of cover assembly  104  and include pivotally mounted latch members thereon (explained further below) for securing cover assembly  104  to socket  102 . Cover assembly  104  is adapted for use with a known pick and place machine for placement of socket  102  on the printed circuit board, and further is adapted to prevent warping and deformation of socket  102  during heating, such as during a solder reflow process. More particularly, cover assembly  104  includes a reinforcing rigid member  110  therein that is heat resistant and maintains socket  102  in a planar arrangement. Optionally, rigid member  110  is fabricated from a known metal, such as stainless steel into a flat, planar plate according to known processes or techniques. Alternative rigid member  110  may be fabricated from a known ceramic material according to a known process to produce a heat resistant reinforcement member that does not deform during heating and thereby maintains socket  102  in a planar arrangement. 
     FIG. 2  is a top plan view of pick and place cover  120  which receives rigid member  110  therein to form cover assembly  104  (shown in FIG.  1 ). As illustrated in  FIG. 2 , cover  120  is generally rectangular and includes four substantially orthogonal side walls  122 ,  124 ,  126 ,  128  with a planar top surface  130  extending therebetween and including angled corners between the side walls. While the top surface  130  of the cover  120  extends entirely between side walls  122 ,  124 ,  126 ,  128 , it is understood that top surface  130  may include one or more openings therethrough in alternative embodiments without departing from the scope and spirit of the instant invention. 
   In an exemplary embodiment, one side wall  122  includes hinge elements  132 ,  134  extending therefrom, while the remaining three sides walls  124 ,  126 ,  128  include latch elements  136  depending outwardly therefrom. Side walls  124 ,  126 ,  128  further include brackets  138  extending upward above the top cover surface  130  and extending inward toward one another over a portion of the top surface  130 . Each hinge element  132 ,  134  includes a respective slot  140 ,  142  for receiving projections  108  along one side of socket  102  (as shown in FIG.  1 ). Brackets  138  form a pocket for receiving the rigid reinforcement member  110  (shown in FIG.  1 ). 
   Latch elements  136  on the cover  120  are arranged in pairs along side walls  124 ,  126 ,  128  and are disposed symmetrically on either side of lateral and longitudinal axes  144 ,  146  extending through a center  148  of cover  120 . Each latch element  136  includes a latch beam  150  extending substantially parallel to respective side walls  124 ,  126 ,  128 . Each latch beam  150  is joined to the side walls  124 ,  126 ,  128  by a web  152  projecting substantially perpendicularly to the side walls  124 ,  126 ,  128 . Latch beams  150  include grip portions  154  on lateral ends thereof. The grip portions  154  are located adjacent the cut-out corners of cover surface  130 . The latch beams  150  also include rounded pivot ends  156  that are located adjacent cover axes  144 ,  146 . In an exemplary embodiment, and as illustrated in  FIG. 2 , grip portions  154  extend inwardly from latch beams  150 . As explained below, grip portions  154  resiliently receive projections  108  of socket  102  (shown in  FIG. 1 ) and maintain the projections  108  between grip portions  154  and side walls  124 ,  126 ,  128 . 
     FIG. 3  is an end elevational view of cover  120  to better illustrate brackets  138  extending upwardly from and extending over cover top surface  130 . Each bracket  138  includes a slot  170  that receives an edge of rigid member  110  (shown in  FIG. 1 ) in an interference fit to securely retain the rigid member  110  in a planar position with respect to cover  120 . Thus, when cover assembly  104  (shown in  FIG. 1 ) is engaged by vacuum pickups of a pick and place machine, cover  120  and rigid member  110  are maintained in their respective planar orientations, thereby imparting structural strength and stiffness to socket  102  (shown in  FIG. 1 ) to resist heat-related stresses and deformation during solder reflow operations when surface mounting the electronic package. 
   As also illustrated in  FIG. 3 , latch members  136 , and more specifically, latch beams  150  are elevated above cover surface  130  at pivot ends  156 . As such, pivot ends  156  are located above rigid member  110  when the rigid member  110  is received in brackets  138 . This clearance of the rigid member  110  allows pivot ends  156  to be actuated as explained below to release cover assembly  104  from the socket  102  after being soldered to the printed circuit board. 
   In an exemplary embodiment, cover  120  is integrally fabricated according to a known process, including but not limited to a molded piece fabricated from a high temperature nylon material A unitary construction suitable for transferring structural rigidity of rigid member  110  to socket  102  to maintain socket  102  in a planar relationship to the printed circuit board is thereby provided. It is contemplated, however, that other known materials (e.g. injection molded plastic and thermoplastic materials, metallic materials and alloys, and ceramic materials) and processes appropriate for those materials may be used in lieu of plastic molding to produce cover  120  in both integral construction and constructions of multiple pieces. 
     FIG. 4  is an exploded perspective view of rigid member  110  and cover  120 . The rigid member  110  is fabricated into a planar element complementary in shape to the top surface  130  of the cover  120 , and is dimensioned to a sufficient thickness to resist warping stresses in socket  102  and prevent deformation of socket  102  during heating. The rigid member  110  slides over top surface  130  and is snugly engaged in brackets  138  to complete cover assembly  104  (shown in FIG.  1 ). Due to the structural strength and rigidity of rigid member  110 , the cover  120  need not be as structurally rigid as it would otherwise. Accordingly, cover  120  may be fabricated from less costly materials in a less costly manner while still ensuring that socket  102  is maintained in a coplanar relationship with the printed circuit board. 
     FIG. 5  is a top plan view of package  100  (shown in  FIG. 1 ) illustrating cover assembly  104  attached to socket  102  in a latched position. The latch elements  136  are fitted over respective socket projections  108  along one side of the assembly  100 . Along the remaining sides, socket projections  108  are received between outer surfaces of side walls  124 ,  126 ,  128  and grip portions  154  of latch elements  136 . Rigid member  110  is received in brackets  138  and provides a sturdy reference plane to maintain socket  102  in a planar orientation and to counteract the tendency of the socket  102  to deform during solder reflow operations. When cover assembly  104  is attached to socket  102  in the latch position, package  100  may be positioned on a printed circuit board with a pick and place machine, and socket  102  may be surface mounted to the printed circuit board with a solder reflow operation. 
     FIG. 6  is a magnified view of a portion of package  100 . The grip portion  154  includes a tapered shelf  180  extending beneath a lower surface  182  of one of socket projections  108 . Thus, latch element  136  forms a wrap-around engagement with socket projection  108 . Hence, when cover assembly  104  is lifted for positioning on a printed circuit board, tapered shelves  180  of latch elements  136  afford support from beneath socket projections  108 . Gravitational forces tending to separate the cover assembly  104  and socket  102 , when package  100  is lifted, are therefore counteracted. Accordingly, the socket  102  is maintained in a desired position relative to cover assembly  104 . 
   A bottom surface of the grip portion  154  in  FIG. 6  is located to extend a predetermined distance above the printed circuit board once the socket  100  is installed. For example, in one embodiment, a vertical clearance of greater than 2.0 mm is provided so that desired electrical components may be located underneath the grip portions  154  when the package  100  is installed on a circuit board. It is contemplated that greater or lesser clearances and other dimensional variations may be used for alternative installations of package  100 . 
     FIG. 7  is a top plan view of electronic package  100  illustrating cover assembly  104  in an unlatched position for removal from socket  102  once solder reflow operations are complete. Latch elements  136  are actuated to the unlatched position by depressing pivot ends  156  inward toward respective side walls  124 ,  126 ,  128 . As pivot ends  156  are depressed, latch beams  150  are pivoted about webs  152  where the latch elements  136  are attached to the side walls  124 ,  126 ,  128 . In turn, grip portions  154  are deflected outwardly and away from respective side walls  124 ,  136 ,  128  until projections  108  are released from the grip portions  154 . Once projections  108  are released, the cover  104  may be rotated upward about hinge elements  132 ,  134  (as shown in  FIG. 1 ) until hinge elements  132 ,  134  are released from tab projections  108  and the cover assembly  104  may be removed. When the cover assembly  104  is removed, the socket  102  remains in secure mechanical and electrical connection to the printed circuit board in a planar relationship thereto. 
   Likewise, cover assembly  104  may be latched to socket  102  by inserting hinge elements  132 ,  134  socket projections  108  on one end of the socket  102 , and rotating the cover assembly  104  downward about hinge elements  132 ,  134  toward socket  102 . By depressing pivot ends  156 , grip portions  154  are deflected outwardly as latch beams  150  pivot about webs  152 . Hence, socket projections  108  may be aligned between side walls  124 ,  126 ,  128  and grip portions  154  as shown in FIG.  7 . When the pivot ends  156  are released (i.e., not depressed) latch elements  136  resiliently return to the latched position (shown in  FIG. 5 ) wherein cover assembly  104  is securely engaged to the socket  102 . 
   In an illustrative embodiment, flexibility of the latch elements  136  to pivot about webs  152  is provided by the molded properties of the cover  120 . In particular, the webs  152  are resilient in one direction (as denoted by arrow A in  FIG. 7 ) to allow resilient flexing of latch elements  136  to latch or unlatch the cover assembly  104  to the socket  102 . The arrow A represents an actuator path about an axis of rotation extending perpendicular to the plane containing the rigid member  110 . In addition, the webs  152  are appreciably stiff in other directions to impart structural strength to the socket  102  to resist deformation of the side walls  124 ,  126 ,  128  along the axis of rotation. Specifically, webs  152  are stiff in a direction perpendicular to the surface of cover  120 , together with side walls  124 ,  126 ,  128 . As such, the rigid member  110  of the cover assembly  104  provides horizontal and vertical stiffness to the socket  102 , while the cover  120  provides vertical stiffness to the socket  102  to maintain socket  102  in a planar position and orientation with respect to the printed circuit board. 
   According to another aspect of the present invention, and in an illustrative embodiment, the cover assembly  104  is configured to be maintained within a predetermined envelope  200  (shown in phantom in  FIG. 7 ) regardless of whether the cover  120  is in the latched position (shown in  FIG. 5 ) or the unlatched position (shown in FIG.  7 ). Interference of the latch elements  136  with other circuit board components is therefore avoided, and space on the printed circuit board is preserved. In an exemplary embodiment, envelope  200  is a square. It is appreciated that other design envelopes of various shapes and sizes may be provided in alternative embodiments and other applications of package  100 . 
     FIG. 8  is a perspective view of another embodiment of a cover assembly for an electronic package  250  including a stiffening cover or frame  254  situated about a socket  256  and maintaining socket  256  in a coplanar position relative to a printed circuit board. The frame  254  includes multiple walls  258  extending generally complementary to the outer profile of the socket  256 , and the socket  256  is received in the frame  254 . Once the socket  256  is received in the frame  254 , the socket and frame assembly is then located on the printed circuit board (not shown in  FIG. 8 ) for solder reflow operations as described above. As illustrated in  FIG. 8 , the socket  256  includes oppositely positioned C-shaped elements contained in either end of the socket frame  254  and connected to one another. The C-shaped elements of socket  256  defines a cross-shaped opening  262  therebetween. It is contemplated, however, that in alternative embodiments the socket  256  may assume a variety of shapes defining various openings therebetween to accommodate various socket applications. 
   In an exemplary embodiment the socket  256  is fabricated from, for example, injection molded plastic according to known techniques, while the frame  254  is fabricated from metal. As such, the frame  254  is fabricated from a much stiffer or rigid material than the material from which the socket  156  is fabricated. The stiffness of the frame  254  resists heat related stress and deformation and maintains the socket  256  in a planar orientation relative to the printed circuit board. Further, in various embodiments, the frame  254  and the socket  256  may be fabricated from any of the foregoing materials and processes to produce suitable stiffness to resist deformation during solder reflow processes. 
     FIG. 9  is a partial cross sectional view of a portion of the electronic package  250  illustrating an exemplary tongue-in-groove latch connection of the socket  256  within the frame  254 . A side wall  258  of the frame  254  abuts against the socket  256  and retains the socket  256  in a planar position. Specifically, a tongue  280  extends laterally outward from the socket  256  and is received in a groove  282  extending on the interior portion of the frame  254 . While in the illustrated embodiment the tongue  280  extends from an edge of the socket  256  and is received in the groove  282  extending in the interior surface of the frame  254 , it is appreciated that in an alternative embodiment a tongue extending from the frame  254  could be accommodated by a groove in an edge of the socket  256 . The tongue and groove arrangement may extend wholly or partially around the mating surfaces of the socket  256  and the frame  254  to provide a suitable latching engagement of the socket  256  and frame  254 . 
   It is contemplated that in further and/or alternative embodiments, other connection and latch arrangements familiar to those in the art may be used to attach the socket  256  to the frame  254 . Additionally, the socket  256  and/or the frame  254  may exhibit flexiblity to install and remove the socket  256  to the frame  254  while achieving a sufficient rigidity to withstand solder reflow operations without deformation. As such, associated nonplanarities of the socket and the printed circuit board are avoided. 
   While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.

Technology Category: 4