Patent Document

CROSS-REFERENCE TO RELATED APPLICATION 
   This is a divisional application of U.S. Ser. No. 11/365,366, filed Mar. 1, 2006, now U.S. Pat. No. 7,331,796, which claims benefit to U.S. Ser. No. 60/715,261, filed Sep. 8, 2005. 

   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   This invention was made with United States Government support under Contract No. NBCH3039004, DARPA, awarded by the Defense, Advanced Research Projects Agency, whereby the United States Government has certain rights in this invention. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to the provision of novel and unique Land Grid Array (LGA) interposers, which incorporate the structure of metal-on-elastomer hemi-torus and other geometrically configured electric contacts to facilitate an array of interconnections between diverse electrical components. The invention is further concerned with a method of producing the inventive LGA interposers. 
   Land Grid Array (LGA) interposers, by way of example, provide an array of interconnections between a printed wiring board (PWB) and a chip module, such as a Multi-Chip Module (MCM), among other kinds of electrical or electronic devices. LGA interposers allow connections to be made in a way which is reversible and do not require soldering as, for instance, in ball grid arrays and column grid arrays. Ball grid arrays are deemed to be somewhat unreliable on larger areas because the lateral thermal coefficients of expansion driven stresses that develop exceed the ball grid array strength. Column grid arrays hold together despite the stresses but are soldered solutions and, thus, do not allow for field replaceability, which is important because it saves the customer or user significant costs in the maintenance and upgrading of high-end computers for which LGAs are typically used. 
   2. Discussion of the Prior Art 
   The basic concept of utilizing LGA interposers to provide an array of electrical connections is well known in the technology. In this connection, reference may be made in particular to Hougham, et al., U.S. Patent Publication No. 2005/0106902 A1, which is commonly assigned to the assignee of this application, and the disclosure of which is incorporated herein by reference in its entirety. This publication describes LGA interposers which define structure consisting of metal-on-elastomer type electrical contacts, wherein a compliant contact consists of an elastomeric material structural element partially coated with an electrically conductive material, preferably such as a metal, so as to form the intended electrical contact. However, there is no disclosure nor suggestion of a compliant contact of an LGA interposer type providing multiple points of electrical contact for each gridpoint in a configuration, such as is uniquely provided by the present invention. 
   Johnescu, et al., U.S. Patent Publication No. 2005/0124189 A1 discloses an LGA-BGA (Land Grid Array-Ball Grid Array) connector housing and electrical contacts which, however, do not in any manner disclose the novel and inventive LGA interposer metal-on-elastomer structure as provided for herein. 
   Similarly, DelPrete, et al., U.S. Pat. Nos. 6,790,057 B2 and 6,796,810 B2; and Goodwin, et al., U.S. Pat. No. 6,293,810 B2, describe various types of elastomeric electrical contact systems and devices which, however, do not at all disclose the features and concept of the present inventive metal-on-elastomer LGA interposers and arrays pursuant to the present invention. 
   SUMMARY OF THE INVENTION 
   Metal-on-elastomer type LGA contacts, as described hereinabove, have been previously described in Hougham, et al. in which a compliant contact consists of a structural element of a non-conductive elastomer that is coated on a part of its surface with electrically conductive material, which resultingly forms the electrical connection. However, a compliant contact with multiple points of electrical contact for each gridpoint is only disclosed by the present invention, wherein several specific geometries and variants are also described. Among these, a hemi-torus shaped element, such as being similar in shape to one-half of a sliced donut in transverse cross-section) may be oriented concentrically with respect to a via (or proximate thereto), the latter of which passes through an insulating carrier plane to the other side thereof. Metal is deposited onto the external portions of the hemi-toroidal elastomer element in order to form a multiplicity of electrically conductive contacts. 
   There are two general instances of LGA interconnects made with hemi-toroidally shaped, or other kinds of structural contact elements constituted of elastomeric materials. In the first instance, holes or vias in an insulating carrier plane would first be filled with metal to form solid electrically conducting vias with a surrounding pad or dogbone pad. Onto these pads would be molded both top and bottom elastomeric LGA bodies possessing various shapes, for example, hemi-toroidal. Then in a final step, metal strips would be deposited from the via pad on each side up and over the apex or uppermost ridge of the elastomeric hemi-torus. As illustrated in the drawings, this would then form a continuous electrical path from the highest point on the top hemi-torus shape to the lowest point on the bottom hemi-torus shape at several points for an individual I/O. 
   In the second instance, the insulating carrier is initially unmetallized with open holes on the desired grid pitch. Then, the top and bottom elastomeric bodies, for instance, hemi-toruses are molded and metallization follows to form the electrically conducting path, as illustrated hereinbelow. In case that during molding, the open hole in the insulator were inadvertently (or purposely) filled with elastomer, (e.g. siloxane), this can be removed in a controlled fashion by a coring or punch step to open a continuous pathway from the top surface to the bottom surface. Metallization can then be deposited on the exposed surface, which is produced thereby in a desired pattern so as to form the electrically conductive pathway. 
   In addition to the standard two-sided LGA interposer, i.e., on both sides of an insulating carrier phone, a one-sided compliant contact is also generally known in the art, and referred to as a “hybrid” LGA in which the contacts are soldered (ball-grid-array or BGA) to the circuit board but form a compression connection with the module, as in Jobnescu, et al., this frequently being referred to as a “hybrid BGA/LGA” or a “hybrid LGA/BGA” interposer. 
   There are several types of hybrid BGA/LGA&#39;s commercially available; however, the present invention describes a new type of hybrid BGA/LGA combining a metal-on-elastomer hemi-toroidally shaped top or upper contact with a solderable (BGA) bottom or lower contact. This provides significant advantages over existing technologies, and examples thereof are presented hereinbelow. 
   In one preferred embodiment, an insulating carrier plane with regularly spaced through-holes is treated to create a metal pad on top to fill the holes with electrically conducting metal for a through via, and a bottom surface, for example, by electroplating followed by photolithography. This produces a bottom surface with a pad for a BGA connecting to a circuit board. Then molded onto the top surface is a hemi-toroidal shape of an elastomeric material, such as siloxane rubber. The hemi-torus is located concentric to the metal via pad and surrounds it either fully or partly so that the elastomeric inside edge of the hemi-torus either touches the metal via and pad or lies outside the boundary of the via and pad. Then, metal is deposited to form a path of a continuous electrical connection leading from the top of the elastomer hemi-torus to the pad, which connects to the electrically conducting via to the bottom side of the insulating carrier plane creating a continuous conductive pathway from top to bottom. The metal on the elastomer may be distributed over the entire surface, or fabricated to consist of one or more strips connecting the top of the hemi-torus to the via pad. In a preferred embodiment there can be employed three strips, separated by 60 degrees from one another, although other quantities and spacing are shown herein. All of the strips start at the top of the torus, or slightly on the outside edge, and terminate on the pad in the center, this then providing multiple contact points, which is deemed electrically desirable. 
   Entrapment of air in the center of the hemi-torus is of concern as it could interfere with reliable seating of the electrical contact in compression. This potential concern can be mitigated by forming an opening or venting slit in the side of the torus during or after molding. Alternatively, any concern about entrapped air can be overcome by making the metal strips which extend over the top of the hemi-torus thick enough to extend over the elastomer surface, so that the gap produced between the uncoated area of the hemi-torus and the module bottom when the metal is in contact with the module bottom provides sufficient venting to allow a facile escape of air from the center of the hemi-torus upon actuation. 
   Another advantage to having multiple discontinuities in the hemi-torus shape resides in that each segment with its metal strip contact can move independently and better accommodate or compensate for non-uniformities in the mating surfaces. 
   The hemi-toroidal shape of the interposer can be molded from a compliant (rubbery) material onto each I/O position in an array, and metal strips are fabricated on the top surface of this shape so that they will provide multiple electrical pathways from a single chip module pad to a single printed circuit board pad. When this compliant hemi-torus is thus metalized, and preferably provided with discontinuities in the donut wall so that air would not be trapped preventing good contact, and provided that the compliant button stays well adhered to the insulating substrate or plane by virtue of anchoring holes, surface roughening, or surface treatments or coatings, then a uniquely functioning LGA is readily produced. 
   A structure pursuant to the invention possesses another advantage. For modules or PCBs that have solder balls or other protruding conductive structures, the LGA interposer array can be actuated into the module/PCB sandwich without the need for any separate alignment step or alignment structures. The ball will nest in the hemi-torus structure and center and stabilize itself with respect to any lateral motion in the x-y directions. 
   This provides another advantage which may sometimes be invoked, in that a module, which has had solder balls attached thereto, it in preparation for an ordinary BGA solder reflow step could instead be redirected on the assembly line for utilization in an LGA socket. Thus, a single product number part (balled module) could be used in two separate applications: 1) BGA soldering and 2) LGA socketing. 
   Such torus structures could be made by molding where the molds are made by drilling or machining with a router-like bit. Alternatively, it could be made by chemically or photoetching of the mold material utilizing a mask in the shape of a torus structure. The mask could be made by photolithography directly on the mold die or could consist of a premade physical mask (such as from molybdenum sheet metal) that was separately formed by photolithography and then applied to the mold die. 
   Another embodiment of this invention utilizes a hemi-torus that has been divided into three or four sections, each of which have been metalized to provide separate electrical paths, and whereby each section can respond mechanically independently when contacted with a pad or solder ball and can thus more reliably form a joint. Moreover, preferably a small space between these sections is created to allow gas to escape freely. 
   Pursuant to yet another embodiment, a number of the divided sections of a single hemi-torus can be made taller to provide a lateral stop for the case when a balled module is loaded preferably from one side thereof. 
   According to another embodiment, a wall shape of the sectionally-divided hemi-torus curves back in and under to form a nest so that when a solder ball is brought into contact therewith, it can be pressed down into the nest and snapped into place, or the shape could be curved simply to best nest a solder ball held in place there against. 
   As described in another embodiment, the I/O consists of multiple hemi-toroidal conic sections or domes that are fabricated into a group to service a single I/O. Each of these domes is metalized separately so that when contact is made with a module pad, redundant electrical paths are formed. The different contacts can also act independently mechanically thus being better able to accommodate local non-uniformities. A further modification would be to make a portion of the hemi-toroidal domes in such a group higher in the z-direction, thus providing a mechanical stop for cases where a balled module is loaded in part from one side, and thus able to constitute an alignment feature. 
   In the above embodiments, the structures and methods described can be applied to either single sided compliant LGAs (aka hybrid LGA), i.e., on one side of the carrier plane only, or to double sided LGAs. Further, they can be applied to hybrid cases where the corresponding metal pad is either directly in line with the center axis of the upper contact or may be offset therefrom. 
   As shown in another embodiment, the compliant structures are in a linear form rather than based on a torus or groups of domes. From a linear compliant bar, or alternatively a sectioned bar, multiple contact strips can be formed for each I/O. Further, the multiple metal contact strips could be located on different linear bars for a given I/O. Various arrangements could include multiple metal strips on the same linear section of compliant material, or on different adjacent linear bars in a line, or on different linear bars on either side of the central I/O via. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Reference may now be made to the following detailed description of preferred embodiments of the invention, taken in conjunction with the accompanying drawings; in which: 
       FIG. 1  illustrates generally diagrammatically, a metal-on-elastomer LGA interposer array, shown in a transverse sectional view, pursuant to a first embodiment of the invention; 
       FIG. 2A  illustrates a modified embodiment of the metal-on-elastomer LGA interposers, shown in a transverse enlarged sectional view; 
       FIG. 2B  illustrates a perspective view of the LGA interposer array of  FIG. 2A ; 
       FIG. 3  illustrates a perspective view of metal-on-elastomer LGA interposers; 
       FIG. 4  illustrates a transverse enlarged cross-sectional view of the LGA interposers of  FIG. 3 ; 
       FIG. 5  illustrates a perspective view of a further embodiment of an LGA interposer array; 
       FIG. 6  illustrates a transverse enlarged cross-sectional view of the interposer array of  FIG. 5 ; 
       FIG. 7  illustrates a perspective view of a further embodiment of a metal-on-elastomer LGA interposer array; 
       FIG. 8  illustrates a transverse enlarged cross-sectional view of the LGA interposer array of  FIG. 7 ; 
       FIG. 9  illustrates a perspective view of a still further embodiment of a metal-on-elastomer LGA interposer array; 
       FIG. 10  illustrates a perspective view of a further embodiment of an LGA interposer array, which is similar to that illustrated in  FIG. 7 ; 
       FIG. 11  illustrates a further embodiment in a perspective view of an LGA interposer array showing a modification relative to that shown in  FIG. 10 ; 
       FIG. 12  illustrates a perspective representation of a further LGA interposer array, which is somewhat similar to that of  FIG. 10 ; 
       FIG. 13  illustrates a transverse enlarged cross-sectional view of the LGA interposer array of  FIG. 12 ; 
       FIG. 14  illustrates a perspective view of a further embodiment of an LGA interposer array; 
       FIG. 15  illustrates a transverse enlarged cross-sectional view of a portion of the LGA interposer array of  FIG. 14 ; 
       FIG. 16  illustrates a transverse enlarged cross-sectional view of an embodiment which is somewhat similar to that of  FIG. 14 ; 
       FIG. 17  illustrates a perspective view of a further embodiment of an LGA interposer array; 
       FIG. 18  illustrates a transverse enlarged cross-sectional view of the LGA interposer array of  FIG. 17 ; 
       FIG. 19  illustrates a perspective view of a modified embodiment of the LGA interposer array, relative to that shown in  FIG. 17 ; 
       FIG. 20  illustrates a transverse enlarged cross-sectional view of a portion of the LGA interposer array of  FIG. 19 ; 
       FIG. 21  illustrates a modified arrangement consisting of linear bars of metal-on-elastomer contacts shown in a perspective representation; 
       FIG. 22  illustrates a transverse enlarged cross-sectional view of a portion of the LGA interposer arrangement of  FIG. 21 ; and 
       FIGS. 23-25  illustrate, respectively, alternative-processing concepts for providing the LGA interposer arrays in accordance with various of the embodiments described hereinabove. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In the detailed description of the various embodiments, elements or components, which are substantially similar or identical, are designated with the same reference numerals. 
   Referring to the embodiment of the metal-on-elastomer LGA interposer array  10 , as illustrated in  FIG. 1  of the drawings, there are shown a plurality of the interposers  12  in the form of hemi-toroidally shaped elements or so called buttons (generally simulating the shape of a transversely sliced donut). Each of the LGA interposer buttons  12  includes a plurality of circumferentially spaced flexible strip-like metal elements  14  forming electrical contacts which reach from the topmost surface  16  of each respective LGA button  12  to the via  18  which extends through an insulating carrier pad  20  on which the LGA interposer buttons are mounted, and down through the center of the LGA buttons so as to connect to a conductive pad  22  which surrounds through the through via on both sides of the carrier  20 , and extends out along the insulating carrier surface beneath the LGA so as to make electrical contact at the other side or the lowermost end surface  24  of the inversely positioned lower LGA interposer buttons  26 . The electrically-conductive flexible metal elements are primarily strips  14  which extend from the uppermost end of the respective upper LGA interposer buttons  12  inwardly into an essentially cup shaped portion extending to the hole or via  18  formed in the pad  22 . 
   Consequently, by means of the pads  22 , which are constituted of electrically conductive material or metal and which surround each of the through vias  18  formed in the dielectric material insulating carrier plane  20 , these contact the ends of each of the metal strips  14 , which extend along the external elastomeric material surface of each respective LGA hemi-toroidally shaped interposer structure or button  12 . Accordingly, electrical contact is made from the uppermost or top end of each respective LGA interposer button to the lowermost end  24  of each of the opposite sided LGA interposer buttons  26  at the opposite or lower side of the insulating carrier plane  20 . 
   With regard to the embodiment illustrated in  FIG. 2A  of the drawings, wherein the electrical elements  30  consisting of the strips positioned on the top surface  16  of the respective LGA interposer buttons  12  extend towards the through via  18 , in this instance, there is no electrically conductive pad present as in  FIG. 1 , but rather the metallic or electrically conductive strips  30  forming the flexible metal contacts extend from the uppermost end  16  of the upper LGA interposer buttons  12  down through the via  18 , the insulating carrier plane  20  to the lowermost ends or apices  24  of the lower inverted LGA buttons  26  on the opposite or bottom side of the structure  10 . 
   In essence, in both embodiments, in  FIGS. 1 and 2A , both the upper and lower LGA interposer buttons  12 ,  26  are mirror images and are symmetrical relative to each other on opposite sides of the insulating carrier plane  20 . With regard to  FIG. 2B  of the drawings, this illustrates primarily a perspective representation of the array of the upper LGA interposer buttons  12  positioned on the insulating carrier plane  20 . 
   Reverting to the embodiment of  FIG. 3  of the drawings, in this instance, the flexible metal electrical contacts  34 , which are positioned so as to extend from the upper ends  16  of each of the respective LGA interposer buttons  12  through the via  18  in the insulating carrier plane  20 , as also represented in the cross-sectional view of  FIG. 4 , are designed to have the electrical metal contacts forming a plurality of flexible strips  34 , which extend each unitarily from the upper ends  16  to the lower ends  24  of the hemi-torus shaped buttons  12 ,  26  from above and below the insulating carrier plane  20  in a mirror-image arrangement. Hereby, the multiple, circumferentially spaced metal electrical contact strips  34  extend from the uppermost point on one side of the insulating plane to the lowermost point on the opposite side so as to form electrical through-connections at both upper and lower ends and, in effect, forming a reversible structure  10 . 
   As shown in  FIG. 5  of the drawings, in that instance, each of the hemi-toroidally shaped interposer buttons  12 ,  26 , which are essentially identical in construction with those shown in  FIGS. 3 and 4  of the drawings, have the metal contacts  40  formed so that they extend in a common annular conductive sleeve structure  42  prior to continuing through the via  18 , which is formed in the insulating carrier plane  20  to the upper and lower ends  16 ,  26  of the LGA interposer buttons  24 . In  FIG. 6  of the drawings, these contacts  40  separate only into separated strip-like portions  42  at the extreme uppermost and lowermost ends of the LGA interposer buttons  12 ,  26  and then join together into the essentially annular structure  44  extending through the via  18  formed in the insulating carrier plane  20 . 
   Referring to the embodiment of  FIGS. 7 and 8  of the drawings, these illustrate essentially a structure  50  wherein LGA interposer buttons  12  are arranged only on the upper surface  52  of the insulating carrier plane  20  in a manner similar to  FIG. 1  of the drawings, and wherein the conductive strips  14  contact metallic or electrically-conductive pads  54  extending respectively through each of the through vias  18  formed in the insulating carrier plane  20 . The lower surface of each metal pad  54 , in turn, may have a solder ball  56  attached thereto in preparation for a subsequent joining, as is known in the technology. 
   As shown in the perspective representation of  FIG. 9  of the drawings, in that instance, the LGA interposer array structure  60 , which is mounted on the insulating carrier plane  20 , is similar to that shown in  FIGS. 7 and 8  of the drawings; however, a slit  62  is formed in the elastomeric material of each LGA interposer button  12 , communicating with the interior  64  thereof, and with the through via  18 , which is formed in the insulating carrier plane  20 , so as to enable any gasses or pressure generated to vent from the interior thereof to the surroundings. 
     FIG. 10  of the drawings is also similar to the structure shown in  FIG. 7 , however, in this instance, each elastomeric interposer button  12  has a plurality of slits  62  or discontinuities formed in the annular toroidally-shaped walls thereof, preferably intermediate respective flexible metal strips  14 , which are located on the upper and inward downwardly extending surface of each elastomer buttons, so as to enable each separate segment  68  to be able to resiliently or flexibly respond to changes or irregularities in the topography of elements contacting the LGA interposer buttons  12 . Also, each segment  68  between each of respective metal contact strips  14  may respond mechanically or independently, so as not to only accommodate differences in topography with a mating surface or differences in the shape of mating solder balls, but in cases where a solder ball will be pressed against the toroidal contacts to produce an electrical connection. In effect, this will enable a mechanical or physical compensation for encountered differences in contact surfaces. 
   With regard to the embodiment of  FIG. 11  of the drawings, which is somewhat similar to  FIG. 10 , in that instance, at least one or more of the segments  68 , which are separated by the intermediate slits extending through the LGA interposer buttons are different in height, so as to have some of the segments  70  higher than others in a z- or vertical direction relative to the plane of the insulating carrier plane  20 . In this instance, two segments  68  of the four independent segments of each respective LGA interposer button  12  are shown to be lower in height than the other segments  70 . 
   With regard to  FIG. 12  of the drawings, in this instance, the array structure  74  of the hemi-toroidal LGA interposer buttons  76 , which are mounted on the insulating carrier plane  20 , the opposite or lower side  78  of which has solder balls  80  connected to electrically-conductive pads  82  extending through the vias  18 , has the centers  84  of the respective LGA interposer buttons  76 , which have electrical strip-like contacts  88  extending downwardly, as shown in  FIG. 13 , have a contoured inner wall configuration  90 , which allows for nesting or a snap-fit with a solder ball (not shown), which may be brought into engagement therewith. In this instance,  FIG. 13  showing the cross-sectional representation of  FIG. 12 , illustrates the knob-shaped interior sidewall profile  90  of the compliant interposer button with the separate metal contact strips  88  extending upwardly along the interior of wall  90  to the topmost end  92  of each respective LGA interposer button  76 . 
   As illustrated in the embodiment of  FIG. 14  of the drawings, in this instance, as also shown in cross-section in  FIG. 15 ; multiple metal strip contacts  88  extend from the top surfaces of the compliant LGA button structure  100 , passing over the top surfaces  102  and extending down into the center part of the hole  104  provided in each interposer button  106 , and meeting with a common pad-shaped metal conductor  108 , which extends along the upper surface  110  of the insulating carrier plane  20  under the button in contact with strips  88  and outwardly until reaching a via  112 , which extends the metal pad downwardly through the insulating carrier plane  20  and along the lower surface  114  thereof, so as to contact solder balls  116 . This is illustrated in the cross-sectional representation of  FIG. 15  of the drawings, which also shows a filled injection tube  120  extending through the insulating carrier plane  20  and a residue break off point  122 , where an elastomer portion was separated from an injection port on a mold forming the entire LGA button structure. This embodiment, showing the filled injection tube for the plastic material, is adapted for the method in which the injection molding of elastomeric material is implemented from the bottom side of the insulating carrier plane  20 . 
   As shown in  FIG. 16  of the drawings, which is essentially similar to the embodiment of  FIG. 15 , in that instance, this illustrates a filler injection tube, the mold (not shown) forming the LGA button structure is implemented by injection molding from the top side of the mold, and a residual mass of elastomer  132  can be ascertained extending from the side  134  of the elastic LGA button structure  100  from which it was separated at the injection port of a mold. 
   Also indicated in  FIG. 16  are two types of anchoring holes in the insulating carrier plane  20 , wherein one hole  136  extends all the way through to the other side thereof, and wherein a blob  138  of residual excess molding material penetrates slightly beyond the bottom surface of the insulating carrier plane  20 . Another type of anchoring hole or cavity  140  does not extend fully through the insulating carrier plane  20 , but is formed as a depression in the top surface of the latter, so as to mechanically anchor the elastomeric material of each LGA interposer button to the structure or plane  20 . 
   Reverting to the embodiment of  FIGS. 17 and 18  of the drawings, these show another aspect of providing an LGA interposer array  150  on an insulating carrier plane  20 , wherein a multiple of LGA interposer buttons  152  of essentially conical configurations and their electrical metallic strip contacts  154 , which extend over the topmost ends  156  thereof, service a common I/O electrical contact  158  in the form of a pad on the upper surface of plane  20 . In this instance, the structure incorporates an electrically conductive via  160  extending through the insulating carrier plane  20 , shown in a center of a group of four LGA interposer buttons  102 , as a common meeting point of the metal contact strips  154  on pad  158 , which extend from respectively one each of the top of each LGA button down the side thereof and into the via metallurgy of the structure, towards the bottom of plane  20 , as shown in cross-section in  FIG. 18  of the drawings. 
   Reverting to the embodiment of  FIGS. 19 and 20  of the drawings, which is quite similar to the embodiment of  FIGS. 17 and 18 , in that instance, the primary distinction resides in that at least one or two of the LGA interposer buttons  152  of a respective group thereof has or have a height which differs from the remaining interposer buttons of that group. For example, two or more buttons  152  of each group may be taller than the remaining buttons  164  of that group (of four buttons) in order to essentially create a lateral stop mechanism for a side loading of a module, through such groupings of LGA interposer buttons in respective arrays. In essence, the different heights in the LGA interposer button groups enable a module with an associated solder ball to be brought into contact and aligned by means of lateral insertion, rather than only vertical insertion, wherein the higher LGA interposer buttons provide stops for the solder balls in order to register with the essentially hemi-toroidally shaped elastomeric contacts. 
   Reverting to the embodiment of  FIGS. 21 and 22  of the drawings, in this instance, there is provided an LGA interposer array  170  arranged on an insulating carrier plane  20 , wherein multiple points of contact for each I/O are provided by means of linear bars of elastomeric LGA interposers  172 . This provides a compliant structure on which a plurality of spaced metallic electrical contact strip elements  174  may be positioned so as to extend from the top  176  of each respective interposer bar  172  both above and below the insulating carrier plane  20 , as shown in  FIG. 22 , into electrically sleeve-like conductive vias  178  formed extending through the insulating carrier plane  20  in contact with respective metal strip contacts  180  above and below the insulating carrier plane  20 . In that instance, the metal contact strips  180  may be formed with different shapes, such as one typical contact joining from two separate ships  182  into a single common strip  184  near the top, as clearly illustrated in  FIG. 21 , or joining further down near the via extending through the carrier plane to the other side. Furthermore, three or more contact points for each I/O may be provided and different types of contact elements may be utilized along the bar whereby some types may be more suitable for conduction of signals and others for high amperage power feeds. 
   As illustrated in  FIGS. 23-25 , there are shown alternate process flows for a balled module, wherein a balled module zoo, as shown in  FIG. 23 , can be directed either towards a solder reflow line for normal BGA connection to a PWB, as illustrated in  FIG. 24 , or alternatively, to an LGA interposer assembly  210  where it is assembled by means of a hemi-toroidal LGA and PWB (wiring board) under pressure to make a field replaceable unit, as shown in  FIG. 25  of the drawings. 
   With regard to the configurations of the LGA interposer buttons, these may be of elastic structural members, which are conical, dome-shaped conic sections or other positive release shapes, such as roughly cylindrical or hemispherical, hemi-toroids, and wherein the metal coating forming the electrically conductive contact members or strips terminate at the apices of each of the multiple buttons. 
   Moreover, the elastomeric material, which is utilized for each of the LGA interposer buttons or for the linear shaped elastic structural member (as shown in  FIGS. 21 and 22 ) may be constituted of any suitable molded polymer from any rubber-like moldable composition, which, for example, among others, may consist of silicon rubber, also known as siloxane or PDMS, polyurethane, polybutadiene and its copolymers, polystyrene and its copolymers, acrylonitrile and its copolymers and epoxides and its copolymers. 
   The connectors of the inventive LGA structure may be injection molded or transfer molded onto an insulating carrier plane  20 , and may serve the purpose of mechanically anchoring the contact to the insulating carrier plane and in instances can provide a conduit for the electrical connections which pass from the top surface of the connector to the bottom surface thereof. 
   In addition to connecting chip modules to printed circuit boards, the arrays of the LGA interposer buttons or linear structure may be employed for chip-to-chip connection in chip stacking or for board to board connections, the contacts may be of any shape and produced by injecting the elastomer in the same side as where the elastomer contact will be anchored to the insulating carrier by a hole or holes or vias, which extend through the insulating carrier or by any cavity edge formed into the surface of the insulating carrier. 
   In essence, the molding of the elastomeric material component or components, such as the hemi-toroidal interposer or interposers may be implemented in that the elastomeric polymer material is ejected from the same side at which the interposer will be positioned on the insulating carrier plane, and will be anchored to the insulating carrier plane by means of a hole or holes, as illustrated in the drawings, which either extend completely through to the opposite side of the insulating carrier plane, or through the intermediary of a cavity which is etched or formed into the surface of the insulting carrier plane, which does not extend all the way through the thickness thereof, and wherein any cavity may have flared undercut sidewalls from maximum anchoring ability or by simple surface roughening of the insulating carrier plane. This is clearly illustrated in the embodiments represented in  FIGS. 15 and 16  of the drawings. 
   While the present invention has been particularly shown and described with respect to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in forms and details may be made without departing from the scope and spirit of the present invention. It is therefore intended that the present invention not be limited to the exact forms and details described and illustrated, but fall within the scope of the appended claims.

Technology Category: h