Patent Document

BACKGROUND OF THE INVENTION  
       [0001]     The subject invention relates to a Land Grid Array (LGA) socket and more particularly to a high density socket with precise alignment to an electrical component.  
         [0002]     Various packages or devices exist within the computer industry which require interconnection to a printed circuit board. These devices have lands or balls which are placed on 1.0-mm centerline spacing and below. These devices are profiled with arrays of 50 by 50 and even greater. Given the plurality of lands, their centerline spacing, and given the force applied to each land, this device causes a variety of problems in practice in connection to the printed circuit board.  
         [0003]     Sockets exist within the market for the interconnection of such devices, where the sockets include columns of conductive polymer allowing the interconnection between the devices and the printed circuit boards. However, these devices too can cause some problems. For example, the conductive polymers can creep over time, and after temperature exposure and thermal cycling. Therefore, its elasticity is reduced, and the normal force, which is applied to the contact interface, is also reduced.  
         [0004]     Moreover, as the density of these sockets and interconnects increases, the complexity of maintaining alignment also increases. Many connector sockets attempt to align the contacts with the interconnected components through the housing. As the housings are molded plastic, the tolerance can be such that, the alignment of the contacts is skewed due to the high tolerance of the housing.  
         [0005]     These and other problems are addressed by the present invention.  
       SUMMARY OF THE INVENTION  
       [0006]     The objects of the invention have been accomplished by providing an LGA interconnect, for interconnection to further electrical components, the LGA interconnect comprising a substrate and a plurality of contact assemblies positioned and retained to the substrate for connection with the electrical components. The interconnect further comprises alignment members projecting from the substrate for aligning the substrate relative to at least one of the electrical components.  
         [0007]     The contact assembly comprises a first contact extending from a first side of the substrate and a second contact extending from a second side of the substrate, the first and second contacts defining an array of contacts. The LGA interconnect further comprises a frame housing surrounding the array of contacts. The alignment members are comprised of pins. The pins extend through the frame housing for registration directly to one of the electrical components. The pins are discrete members attached at diametrically opposite positions of the substrate. The frame housing can laterally float relative to the pins. The frame housing is comprised of first and second frame parts attached to each other. The first and second frame parts are attached at marginal edges of the substrate. One of the frame parts includes frame pins projecting through the substrate, while the other of the frame parts includes alignment apertures for receiving the frame pins in a press-fit manner.  
         [0008]     The frame housing further comprises at least one frame support member extending from side edges of the frame housing across the substrate, for supporting the electrical components above the substrate. The frame housing comprises frame support members having a cruciform configuration extending from opposite side edges of the frame housing and extending across the substrate, for supporting the electrical components above and below the substrate. The substrate is substantially rectangular in configuration and the frame support members define quadrants on both sides of the substrate.  
         [0009]     In another aspect of the invention, an LGA interconnect is profiled for interconnection to further electrical components, and comprises a substrate having an upper surface and a lower surface, marginal side edges, and an array of contact receiving openings therein. A plurality of contact assemblies are positioned and retained in the substrate, with a first contact portion position above the upper surface and a second contact positioned below the lower surface. The plurality of contacts define an array of contacts. A frame housing is positioned around a periphery of the substrate. Alignment members project from the substrate for aligning the substrate relative to at least one of the electrical components.  
         [0010]     The alignment members are comprised of pins. The pins extend through the frame housing for registration directly to the electrical component. The are discrete members attached at diametrically opposite positions of the substrate. The frame housing can laterally float relative to the pins. The frame housing is comprised of first and second frame parts attached to each other. The first and second frame parts are attached at marginal edges of the substrate. One of the frame parts includes frame pins projecting through the substrate, while the other of the frame parts includes alignment apertures for receiving the frame pins.  
         [0011]     The frame housing further comprises at least one frame support member extending from side edges of the frame housing across the substrate, for supporting the electrical components above the substrate. The frame housing comprises frame support members having a cruciform configuration extending from opposite side edges of the frame housing and extending across the substrate, for supporting the electrical components above and below the substrate. The substrate is substantially rectangular in configuration and the frame support members define quadrants on both sides of the substrate. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  shows a top perspective view of another embodiment of the LGA interconnect of the present invention;  
         [0013]      FIG. 2  shows a lower perspective view of the embodiment of  FIG. 1 ;  
         [0014]      FIG. 3  shows an exploded view of the various components of the embodiment of  FIG. 1 ;  
         [0015]      FIG. 4  shows a perspective view of a first frame member;  
         [0016]      FIG. 5  shows a lower perspective view of a second frame member;  
         [0017]      FIG. 6  shows an enlarged underside perspective view of the cover of the embodiment of  FIG. 1 ;  
         [0018]      FIG. 7  shows a perspective view of the substrate of the embodiment;  
         [0019]      FIG. 8  shows an enlarged view of the area denoted in  FIG. 7 ;  
         [0020]      FIG. 9  shows a cross-sectional view through lines  9 - 9  of  FIG. 8 ;  
         [0021]      FIG. 10  shows a portion of a stamped lead frame showing the contact portion prior to overmolding the insert;  
         [0022]      FIG. 11  shows the over-molded insert over the lead frame of  FIG. 10 ;  
         [0023]      FIG. 12  shows a side view of the insert shown in  FIG. 11 ;  
         [0024]      FIG. 13  is a cross-sectional view through lines  13 - 13  of  FIG. 12 ;  
         [0025]      FIG. 14  is a cross-sectional view through lines  14 - 14  of  FIG. 12 ;  
         [0026]      FIG. 15  is a cross-sectional view through the insert of  FIG. 12 , after the swaging process;  
         [0027]      FIG. 16  is a view similar to that of  FIG. 8 , showing the pin in the first installed position;  
         [0028]      FIG. 17  is a cross-sectional view through lines  17 - 17  of  FIG. 16 ;  
         [0029]      FIG. 18  is a view similar to that of  FIG. 16 , showing the pin in the next position;  
         [0030]      FIG. 19  is a cross-sectional view similar to that of  FIG. 17 , showing the pin transitioning to the locked position;  
         [0031]      FIG. 20  is a cross-sectional view similar to that of  FIGS. 17 and 19 , showing the pin in the locked position;  
         [0032]      FIG. 21  is a perspective view of the assembled substrate and upper and lower frame members;  
         [0033]      FIG. 22  is a view similar to that of  FIG. 21  from the opposite side thereof;  
         [0034]      FIG. 23  is an enlarged view of a portion of the frame and contact members denoted in  FIG. 22 ; and  
         [0035]      FIG. 24  shows an enlarged view of the central portion of the substrate denoted in  FIG. 22 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0036]     The subject invention relates to a Land Grid Array (LGA) interconnect socket and a method of manufacturing the same. When used herein, the term LGA is meant to define many different interconnects. For example, it could be interpreted to mean a chip interconnected to a printed circuit board. However, it can also mean a board to board interconnect. In this application, the invention will be described by way of an interconnect to a chip.  
         [0037]     With respect first to  FIGS. 1-3 , the LGA interconnect is shown at  2  and includes a frame housing  4  ( FIG. 2 ) comprised of first and second frame members  4 A and  4 B ( FIG. 3 ), a cover  5 , and a substrate  6  which carries a plurality of contact assemblies  8 . With reference now to  FIG. 4 , frame housing portion  4 A will be described in greater detail.  
         [0038]     Frame housing portion  4 A includes frame side wall portions  10 A,  12 A,  14 A, and  16 A. Frame housing portion  4 A further includes extension ears  18 A extending from diametrical corners having pin-receiving apertures  20 A, as will be described further herein. At the other diametrical corners, frame housing portion  4 A includes edges  22 A. Alignment pins  24  extend downwardly from the frame housing  4 A and are substantially cylindrical in cross section. Finally, frame support members  26 A extend between opposing side edges of the frame housing  4 A and is cruciform in configuration having a first member  28 A and a second member  30 A defining quadrants therebetween.  
         [0039]     With respect now to  FIG. 5 , frame housing portion  4 B will be described in greater detail. It should be appreciated that frame housing portion  4 B is complementary to frame housing portion  4 A and is designed to trap therebetween the substrate member  6 . With respect to  FIG. 5 , frame housing portion  4 B includes side edge portions  10 B,  12 B,  14 B, and  16 B. In a similar manner to frame housing portion  4 A, frame housing portion  4 B includes extension ears  18 B extending from diametrical corners having apertures  20 B. The other corners include edges  22 B. Frame housing portion  4 B also includes frame support member  26 B, having support members  28 B and  30 B. Finally, as shown in  FIG. 5 , frame housing portion  4 B includes a plurality of hexagonal openings  32  in an array which matches the array of pins  24  on housing member  4 A.  
         [0040]     With respect now to  FIG. 6 , cover  5  will be described in greater detail. As shown in  FIG. 6 , in an underside perspective view, cover  5  includes side walls  34  and top wall  36  defining an enclosure  38  therein. It should be appreciated that cover  5  is profiled to be received over the combination of frame housing portions  4 A,  4 B and the substrate  6 . Thus, at each corner of cover  5 , an extension portion  40  is provided and is profiled to be received over extension ears  18 A and  18 B. As best shown in  FIG. 6 , these extensions include apertures  42  for alignment purposes with the substrate directly as will be further described herein. In the opposite corners, latch members  46  are provided having latching arms  48 , as best shown in  FIGS. 2 and 6 , and will also be described in further detail herein.  
         [0041]     With respect now to  FIG. 7 , substrate member  6  will be described. As shown in  FIG. 7 , substrate  6  is substantially rectangular in configuration. In fact, as shown in  FIG. 7 , substrate  6  is substantially square in configuration so as to define four equal quadrants, and as defined by bisecting lines  52 ,  54 . Substrate  6  includes side edges  60 ,  62 ,  64 , and  66 . With respect now to  FIG. 7 , substrate  6  includes extension ears  70  at diametric opposite corners of the substrate  6 . With reference now to  FIG. 8 , extension ear  70  is shown in greater detail having an aperture shown generally at  72  having a Figure-8 configuration. Aperture  72  includes an enlarged opening at  74  transitioning into a smaller opening  76  by way of flat transition edges at  78 . A latch member  80  is provided extending into opening  76  opposite a stop edge  82 . Latch  80  includes a chamfered edge at  84  and a latching edge at  86 , as will be described in greater detail.  
         [0042]     As shown in  FIG. 7 , substrate  6  further includes a plurality of apertures  90 , whereby the apertures are defined in an array of quadrants, whereby at the intersection of the quadrants, each of the contacts generally faces the center of the substrate. As shown in  FIG. 7 , each aperture  90  includes end edges  92 , side edges  94  and angled side edges  96 . These apertures are substantially similar to those described in Applicants co-pending, concurrently filed patent application Ser. No. ______, Attorneys Docket 17992. With respect still to  FIG. 7 , apertures  98  are provided, which are in alignment with cylindrical pins  24 , but are larger in diameter than the pins  24 . Substrate  6  further includes a side edge  100  at diametrical corners of the substrate  6 , as will be described further herein.  
         [0043]     With respect now to  FIGS. 10-14 , contact assemblies  108  will be described in greater detail. As shown in  FIG. 11 , contact assembly  108  includes a stamped terminal portion  110  having an overmolded insert member  112  overmolded thereto. As shown in  FIG. 10 , the stamped terminal  110  includes a central portion  114  having an elongate aperture  115 , with contact portions  116  and  118  extending from opposite sides thereof defining contact sections  120  and  122 . With respect now to  FIGS. 11 and 12 , insert  112  is shown molded onto terminal portion  110 . Insert  112  includes a shank portion  128 , end portions  130 , head portion  136 , and projecting portion  140 . However, in addition, insert  112  includes a slot  144 , which as shown in  FIGS. 12 and 13 , extends part way into end portions  130 . Slot  144  defines opposing surfaces  146  and  148 .  
         [0044]     Finally, and with reference again to  FIG. 8 , interconnect  2  includes a locating pin  150  having a cylindrical pin portion  152 , an undercut groove  154 , and a reduced diameter portion at  156 . As shown in  FIG. 9 , at the location of groove  154 , the pin includes flat surfaces at  158  and reduced diameter surfaces at  160 . With the details of the various components described, the manufacturing and assembly of the interconnect  2  will now be described.  
         [0045]     The substrate  6  is manufactured in a similar manner to that described above, with the substrate defined with the characteristics shown in  FIG. 7 . While the substrate could be made from many different materials, such as Mylar, ceramic, plastic, or metal, this embodiment utilizes a stainless steel substrate, where the specific characteristics, such as the apertures  90  and the detail of apertures  98  and  72 , are defined by an etching process. However, it should be recognized that some embodiments could be provided by a stamping process. In either event, in this embodiment apertures  90  are formed in quadrants about the substrate, as mentioned above along bisecting lines  52 ,  54 .  
         [0046]     With respect now to  FIG. 10 , the terminals are provided by a process to define a lead frame similar to that shown in  FIG. 10 . The contacts are defined by a metal having a spring characteristic, such as a beryllium copper, and is shown as being stamped and formed to define its characteristics. However, it should also be appreciated that an etching process could also be incorporated to accommodate tight tolerances as the contact density increases.  
         [0047]     Insert  112 , shown in  FIG. 11 , is now overmolded about the central portion  114  of the contact, whereby elongate aperture  115  is used as a sprue for the molten plastic to ensure a complete molded insert. The aperture  115  also provides for a retention mechanism for the insert longitudinally along the length of the terminal, after the insert  112  has solidified. The contact assemblies  108  are now inserted in their respective passageways  90 , and it should be appreciated that slot  144 , as shown in  FIGS. 12 and 13 , will conform in an overlapping manner with a respective aperture  90  and receive an edge of the aperture  90  therein. The inserts are now swaged in a manner whereby the plastic insert is deformed to a position shown in  FIG. 15 . The insert  112  laterally shifts to position the edge of the aperture  90  within the slot  144 , and with surfaces  142  and swaged projection  180  gripping the opposite edge of the substrate  6 . The overmolded insert  112  and the method of swaging is more fully disclosed in Applicants co-pending, concurrently filed patent application Ser. No. ______, Attorneys Docket Number 17992.  
         [0048]     Alignment pins  150  may now be inserted into their fixed position on substrate  6  by moving the alignment pins  150  from the position shown in  FIG. 8 , to the position shown in  FIG. 16 . It should be appreciated that the diameter of pin portion  152  is less than the diameter of aperture  74  and thus, pin  150  can be inserted into the aperture  74 , as shown in  FIG. 16 , with groove  154  aligned with edges  78 . As shown in the cross-sectional view of  FIG. 17 , at this position, the flat edges  158  can be aligned with edges  78  of aperture  72  and the pin can be moved from the position shown in  FIGS. 16 and 17 , to the position shown in  FIG. 18 . With reference now to  FIG. 19 , when the pin  150  is moved to aperture  76 , the diameter of radiused surfaces  160  is less than the diameter of aperture  76 , and therefore the pin can be rotated in the clockwise sense as viewed in  FIG. 19 , by one-quarter turn, to the position in  FIG. 20 . In this position one flat edge  158  abuts stop edge  82 , and the other flat edge  158  is trapped against edge  86  ( FIG. 8 ) of latch arm  80 . FIG.  18  shows how the latch arm  80  extends into the groove  154  of pin  150 .  
         [0049]     At this stage, all contact assemblies are inserted in, and the locating pins  150  are fixedly secured to, substrate  6 . The frame housing members  4 A and  4 B may now be positioned with respective apertures  20 A,  20 B over the locating pins  150 , which positions the frame support members  28 A,  30 A;  28 B,  30 B ( FIGS. 4 and 5 ) intermediate the quadrants of contact assemblies, as best shown in  FIGS. 21 and 22 . The two frame housing members  4 A and  4 B are press-fit together, due to the interference fit between cylindrical pins  24  ( FIG. 4 ) and their respective receiving apertures  32  ( FIG. 8 ) to provide an interference fit between them, as best shown in the exploded view of  FIG. 23 .  
         [0050]     As best shown in  FIG. 24 , the contact assemblies  8  are assembled in quadrants about the support members  28 B and  30 B to define an array of contacts for interconnection to a further electrical component. It should also be appreciated that the support members  28 A,  30 A;  28 B,  30 B act to both rigidify the substrate  6  as well as to provide for a positive stop position for the electrical component to which the LGA interconnect  2  is applied. Said differently, if the LGA interconnect  2  is applied intermediate to two printed circuit boards, the two circuit boards could be assembled to the interconnect  2 , such that the two printed circuit boards are drawn together to a position where the circuit boards contact the support members  28 A,  30 A;  28 B,  30 B.  
         [0051]     With reference again to  FIGS. 21 and 22 , it should be appreciated that the edges  22 A overlap their respective edges  22 B, thereby defining a latching edge. With the upper device now positioned against frame housing portion  4 A, cover  5  can be positioned over the assembly of the frame housing  4  and substrate  5  and latches  6  ( FIG. 6 ) can latch over the overlapping edge  22 A, as best shown in  FIG. 2 , while at the same time, cylindrical pin portions  152  ( FIG. 7 ) may be received in their receiving apertures  42  ( FIG. 6 ) of cover  5 . An underside perspective view of the embodiment as assembled is shown in  FIG. 2 , with the remainder of pin  150 , and the reduced diameter portions  156  extending from the frame housing portion  4 B for further alignment and connection to, a further electrical device.  
         [0052]     Thus, the contact assemblies  8  have enhanced retention to their substrate  6  by way of the slot  144  ( FIGS. 11 and 12 ) being positioned against an edge of its respective aperture  90  ( FIG. 15 ) which provides for a retention of the plastic insert  112  on both sides of the aperture  90 , against respective surfaces  94  ( FIG. 7 ). Furthermore, the support members  28 A,  28 B;  30 A,  30 B allow for proper positioning of an electrical component against the interconnect  2  providing adequate contact force, but preventing overstressing of the contact assemblies. Furthermore, and as best shown in  FIG. 24 , the contacts are arranged in quadrants such that all frictional components of forces cancel each other out, thereby preventing any lateral forces from being transferred to the interconnected component causing degradation of the electrical connection. Finally, as the alignment pins are accurately secured directly to the substrate, the pins can be used to precisely locate the contacts to the electrical component for connection.

Technology Category: 5