Abstract:
A structure of an enhanced durability interconnector to reliably interconnect modules having high density type contacts, such as found in modules having solder ball connections (SBC), to a connecting article such as a printed circuit board. The structure comprising a means to provide the SBC type contact a mating surface having a wide contact area. Furthermore, the electrical connecting medium within the interconnector, which is embedded in an elastomeric material to provide compliance, is strengthened by using two or more embedded wires in combination for each wide contact area contact. The interconnector is incorporated into a fixture to compress the interconnector between the SBC module and the connecting article. The fixture having further capability to align the connections, control the compression pressure and to prevent over-compression.

Description:
A PROCESS FOR FORMING INTERCONNECTOR MODULES 
     This application is a Div of Ser. No. 08/527,733 Sep. 13,1995, U.S. Pat No. 5,810,607. 
    
    
     FIELD OF THE INVENTION 
     The present invention is directed to an electrical interconnector, in particular the connection of an electrical module to a circuit board, and more particularly to the provision of socket type inter-connection means for modules having contacts suitable for high density applications. 
     BACKGROUND OF THE INVENTION 
     It is a constant endeavor to find ways of increasing the pinout density of integrated circuits (ICs). This is particularly important in ICs with high pin counts and relatively small packages. Solder ball connection (SBC) technology was developed to satisfy this growing need. In general the number of electronic circuits that can be manufactured per unit area of silicon or board space has increased dramatically in recent years. This increase in circuit density has produced a corresponding increase in the number of connections required between the various electronic circuits, integrated circuit modules, and boards to facilitate the manufacture of more complex products. High density integrated circuit modules such as microprocessors are typically housed in a protective package such as a pin grid array (PGA) module, that provides a means of connecting to other electronic circuits on a printed circuit board. PGA modules have an array of metal pins on the bottom side of the package. The 
     PGA module is often connected and disconnected through these pins to a test card to evaluate the individual electronic circuit components before they are assembled into a final product. Connector sockets are available for PGA modules to facilitate the connection and disconnection of the PGA module for service, upgrade, or testing requirements. 
     Solder ball connection (SBC) modules have recently been developed to address the need for more signal and ground connections, higher density packaging, and compatibility with surface mount technology processes. SBC modules are different than PGA modules in that the SBC module uses solder balls instead of metal pins to provide for interconnections between the module and the printed circuit board. Whereas PGA pins are spaced 0.10 inches apart, the solder balls are typically arranged in an area array pattern with 0.05 inch spacing. This close spacing makes it difficult to use previous interconnector technologies for SBC sockets. Thus, although SBC modules have service, upgrade, burn-in and testing requirements similar to PGA modules, SBC interconnecting sockets are not commonly available. 
     Because of the SBC pin densities, a specialized technology such as that generally used in elastomeric connectors is one of the various interconnection technologies that can be used for an SBC socket. The elastomeric connector provides a conductive path through an elastomeric material to connect the solder balls on the SBC module to the contact pads on the printed circuit board. A wide variety of elastomeric connectors are available that use conductive particles or conductive wires embedded in the elastomer material. The electrical, mechanical, and thermal performance of the elastomeric connector can vary significantly depending on the size, shape, orientation, and density of the conductive particles as well as the properties of the elastomer material . An SBC socket has unique requirement which need to be satisfied if the socket is to be useful, reliable and durable. Elastomeric connectors that are suitable for area array interconnections have previously been described. 
     U.S. Pat. No. 4,998,885, issued Mar. 12, 1991 to Beaman et al., is directed to an elastometer area array interposer. It provides for an elastomeric interposer surrounding fine metal wires which extend through the elastomeric materials permanently bonded to a rigid wiring substrate. It is useful for electrically connecting two substrates having high density interconnections. The structure described is comprised of conductive wires embedded in an elastomer material that are permanently bonded to the rigid wiring substrate. The contact interface is comprised of ball shaped gold wire conductors surrounded by an elastomer material. It is specifically adapted to interconnecting with flat gold plated pads on the surface of the mating substrate. The ball shaped contact surface is not large enough for use with an SBC type contact. SBC interconnection with this type of a ball shaped contact surface would cause excessive degradation of the connecting wires and ball shaped contact and limit the durability and reliability of the interface for socket applications. 
     U.S. Pat. No. 5,371,654, issued Dec. 6, 1994 to Beaman et al., is directed to a structure for packaging electronic devices, such as semiconductor chips, in a three dimensional structure. The structure includes a multilayer wiring substrate for X-Y connections along with an elastomeric connector for Z axis connections. The elastomeric connector described is specifically adapted to a three dimensional packaging approach and does not require a contact interface with high durability. Also, the contact interface in this patent is comprised of an elastomeric connector having gold wire conductors mated to flat gold plated pads on the surface of the multilayer wiring substrate. The contact interface on the elastomeric connector would not be compatible for connection to the solder ball on an SBC module. 
     The present invention provides solutions to the unique SBC module interconnecting problems. The following interconnector requirements should be considered in order to satisfactorily connect to a module whose pinouts are solder ball connections. 
     Firstly, the solder ball connections have irregular ball sizes. Additionally, the printed circuit board to which the module is connected has planarity variations of its contact pads. Thus, the interconnector contact interface should have high compliance to enable it to yield elastically when contact forces are applied. 
     Secondly, the SBC interconnector should have a contact metallurgy such that it does not form a high resistance intermetallic layer with the solder balls even for high temperature applications. 
     Thirdly, the interconnector should be such as to minimize deformation of the solder ball while the SBC module is connected to the interconnecting structure. 
     Fourthly, the SBC interconnector contact interface should be of high durability to allow multiple repeated connections and disconnections of the SBC module without degradation. 
     In addition, the SBC interconnector should act as a clamping fixture so as to provide consistent pressure between the SBC module and the interconnector contacts. Preferably, the fixture should include a means of aligning the corresponding contacts on the interconnector with the solder balls on the module and also with the connecting article. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved electrical connecting device. Another object of the present invention is to provide a means for the connecting device to act as a clamping fixture so as to provide consistent pressure between the contacts of a module being interconnected, the interconnecting device and a connecting article. Preferably, the fixture should include a means of aligning the corresponding contacts on the interconnecting device with the module contacts and also with the connecting article. 
     A broad aspect of the present invention is a structure having a dielectric body. The dielectric body has a first surface, a second surface, and at least one embedded conductive member. Each conductive member has a first end extending to or through the first body surface, and a second end extending to or through the second surface. At least one of the ends being enlarged and having a wide top surface area. 
     In a particular aspect of the present invention, an enlarged end is comprised of a grouping means for grouping together a combination of at least two embedded members. 
     In another particular aspect of the present invention, the structure further comprises a compression means: for compressing a solder ball connection on an external component to an enlarged end of the structure; for compressing an enlarged end of an embedded wire to a solder ball connection on an external component; and to compress the other end of the embedded wire to a contact on an external article. 
     In still another particular aspect of the present invention, the structure further comprises a component having at least one solder ball connection making contact with an enlarged end of an embedded wire or wire grouping, and a connecting article having at least one article contact making connection with the other end of the embedded wire or a wire grouping of embedded wires. The structure also has a compression means for compressing the solder ball connection to the enlarged end and preferably to also compress the article contact to the other wire end or wire grouping. 
     In another particular aspect of the present invention, the structure&#39;s compression means further comprises: one or more spacers disposed such as to prevent over compression; one or more contact alignment means to align the structure with a connecting article and/or a connecting component; and/or a stiffener disposed so as to prevent bowing of the external article. 
     Another broad aspect of the present invention is a process to make a structure comprising the steps of: providing an electrically conductive substrate having a periphery, a first substrate surface and a second substrate surface; attaching a first plurality of conductive pads to the first substrate surface; attaching a second plurality of conductive pads to the second substrate surface disposed to correspond with and be opposite to the first plurality of conductive pads and leaving an exposed substrate area on the substrate; attaching at least one conductive member to each of the first plurality of conductive pads, with the conductive member disposed such as to form a free standing structure having a straight end; forming at each straight end an enlarged wire bonding contact having a wide top area surface; placing a dam upon the first surface such as to enclose its periphery, with the dam being disposed such as to surround the conductive members; filling the dam with a dielectric material such as to leave each wire bonding contact exposed at a top face of the dielectric material; and etching away the substrate at its exposed substrate area such as to leave an array of individual button contacts. 
     In a more particular aspect of the process according to the present invention, the enlarged contact is formed by bonding a conductive contact pad to one or more of the wire bonding contacts at the enlarged contact surface, or the enlarged contact is formed by bonding a polymer pad to one or more of the wire bonding contacts at the enlarged contact surface 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a magnified view of a solder ball contact in typical relationship to an unmodified wire bonding contact. 
     FIG. 2 shows a magnified view of a solder ball contact in relationship to a conductive pad contact attached to a single embedded wire. 
     FIG. 3 shows a magnified view of a solder ball contact in relationship to a conductive pad contact attached to a two wire grouping. 
     FIG. 4 shows a magnified view of a solder ball contact in relationship to a polymer contact attached to a single embedded wire. 
     FIG. 5 shows a magnified view of a solder ball contact in relationship to a polymer contact attached to a two wire grouping. 
     FIG. 6 shows a magnified view of a solder ball contact in relationship to wire bonding contact leading from a two wire grouping which is surrounded by a thin layer of flexible polymer. 
     FIG. 7 shows an interconnector fixture using the interconnector of this invention. 
     FIG. 8 shows another interconnector fixture using the interconnector of this invention. 
     FIG. 9 shows an interconnector fixture for a connecting article having SBC type contacts. 
     FIG. 10 shows the application of gold plating to an area array on the substrate. 
     FIG. 11 shows the bonding of wires to the gold plated areas. 
     FIG. 12 shows the formation of laser balls on the bonded wires. 
     FIG. 13 shows the wires enclosed in a casting dam. 
     FIG. 14 shows the etching of the exposed substrate surface. 
     FIG. 15 shows the first interconnector assembly. 
     FIG. 16 shows the second interconnector assembly. 
     FIG. 17 shows a typical stamped substrate on the bonded wires. 
     FIG. 18 shows an expanded view of a stamped substrate. 
     FIG. 19 shows a magnified side view of the second substrate sub-assembly. 
     FIG. 20 shows the third interconnector assembly. 
     FIG. 21 shows a magnified side view of the third substrate subassembly. 
    
    
     DETAILED DESCRIPTION 
     The present invention provides an improved electrical connecting device useable for interconnecting a module having high density type contacts with a printed circuit board or with another module. In particular, this invention is a structure, to be referred henceforth as an interconnector, for the interconnection of a connecting article with a module having contacts preferably of the SBC type. The significance of the SBC interconnector contact area problem is observed by considering the illustration of FIG.  1 . 
     FIG. 1 shows a magnified view of an SBC module  30  mated with an interconnector  10 . The solder ball contact  32  is shown in typical relationship to a heretofore typical elastomeric socket wire bonding contact  16  formed at an end of an embedded wire  17 . The wire bonding contact  16  is 1 to 10 mils in diameter. Thus, the irregular  20  to  40  mil diameter solder ball  32  cannot make reliable or durable contact with the wire bonding contact  16 . It has been found that when the wire bonding contact  16  is not modified or supported, repeated engagements and disengagements with the solder ball contact  32  causes degradation of the wire contact end and its embedded wire. The inventors have shown experimentally that enlarging and/or supporting the top surface area of the wire bonding contact  16  increases the durability and reliability of the interconnector  10 . 
     Experiments have shown that a means to achieve repeated, long term and reliable connectivity is to enlarge the top surface area of the wire bonding contact. Several alternative means are herein described which provide the needed enlarged top surface area. In one means shown in FIG. 2, a conductive contact pad  24  having a wide top-surface-area  13  is attached to each wire bonding contact  16  on the interconnector top surface  23  of interconnector  10 . The contact pad  24  is attached to the wire bonding contact  16  along the pad&#39;s bottom surface  15 . The pad&#39;s bottom surface is generally plated with a noble metal to enable formation of a low resistance attachment. The contact pad&#39;s  24  top surface area  13  makes available to the solder ball a wide area of contact surface area. The top surface area  13  is also generally plated. Compression of the solder ball contact  32  of an SBC module  30  against a contact pad  24  results in a reliable and durable electrical connection. It has also been found that difficulty in providing durable connection and consistent pressure between the SBC module  30  and the interconnector contacts is largely due to the small size and weakness of each individual embedded wire  17  which is used as the interconnecting medium. The medium is inadequate to withstand the long-term and repeated applied pressure from a module&#39;s solder ball contact  32 . A means is desirable for strengthening the interconnecting medium used to make connection with each solder ball contact. 
     A means to strengthen the interconnector medium is to group two or more embedded wires for connection to a common contact pad  24 . A two wire grouping  22  is shown in FIG.  3 . The grouping  22  provides enhanced ability to the embedded wires to withstand the pressure resulting from a compressed connection of the solder ball  32  to the contact pad  24 . It results in an increased strength and compliant connective medium. Combining three or more wires in a grouping for attachment to a common contact pad further strengthens the connecting medium. In a three wire grouping the wires are best attached to the pad to form a triangle. In a four wire grouping the wires are preferably attached to the pads to form a square. 
     A third alternative capable of providing connection of an SBC module to a circuit board and having enhanced durability is shown in FIG.  4 . In this embodiment the conducting contact pad is replaced with a polymer pad  28 . Use of a polymer pad enhances the overall compliance of the contact. The polymer pad  28  is coated with a metal  13 . The metal coating  13  is attached to make electrical contact with an embedded wire  17 . The metal coating  13  is generally plated with a noble metal. 
     A fourth embodiment combines the attributes of the second and third embodiments by having the polymer pad  28  enclose two or more wire bonding contacts  16  to form a wire group  22  as shown in FIG.  5 . The enclosed wire bonding contacts  16  are all attached to make electrical contact with the common metal coating  13 . This provides both a wide top end contact area for the solder ball contact  32  and also increases the strength, compliance and durability of the connecting medium which is a wire group  22  rather than an individual wire  17 . 
     FIG. 6 shows a magnified view of another alternative means for an interconnector with enhanced durability. It uses a thin layer of flexible polymer  26  placed upon the top surface  23  of the interconnector  10 . The polymer is made to surround and essentially captivate the wire bonding contacts. Increased strength results when the polymer surrounds and captivates together two or more wire bonding contacts. FIG. 6 shows a two wire grouping. The wire bonding contact  16  on the end of the conductor wire  17  should have its top surface exposed and is best placed to be flush with the polymer surface  27  of the layer of polymer  26 . The exposed wire bonding contact should be able to make direct electrical contact with the solder ball  32  on the SBC module  30 . The thin layer of polymer distributes the contact force from the solder balls  32  on the SBC module over a wider area of the polymer surface  26  thereby preventing excessive deformation of the wire grouping  22  in the dielectric material  21 . The dielectric material  21  is generally an elastomeric material. 
     In the present invention either or both ends of an embedded wire may have an enlarged end. An enlarged end may be attached to a single embedded wire or to a grouping means for grouping together a combination of at least two embedded members at the enlarged end. This is applicable when the grouping means is comprised of a conductive pad, or when the grouping means is comprised of a polymer pad which has a metallic coating which makes electrical contact with the enlarged end, especially when the coating is a metal selected from the group consisting of Au, Pd, Pt, or one of their alloys, or when an enlarged end extends to or through the body surface at a surface location wherein the grouping means is comprised of a polymer layer disposed over a body surface, and wherein the polymer layer has a hole corresponding to the surface location. 
     The enhanced durability connection methods described are best employed when the interconnector includes a fixture which can provide controlled connectivity of the SBC module to the connecting article. Therefore another object of the present invention is to provide a means to the connecting device to act as a clamping fixture so as to provide consistent pressure between the contacts of a module being interconnected, the interconnecting device and a connecting article. Preferably, the fixture should include a means of aligning the corresponding contacts on the interconnecting device with the module contacts and also with the connecting article. 
     FIG. 7 shows an embodiment of such a fixture  40 . The interconnector  10  is held by a dam  20  in a position such that its lower laser ball contacts  25  are aligned with printed circuit board pads  61  on the connecting article  60 . The SBC module  30  is positioned such that its solder balls  32  are aligned with the contact pads  24 . A top plate  55  is placed over the SBC module  30 . The entire assembly is held in place with fasteners  56  such as the nut and bolt shown in FIG.  6 . 
     FIG. 8 shows improvements that can be made to the fixture  50 . These include the use of a cushion  52  between the SBC module  30  and the top plate  55 . The cushion is a polymer cushion  52  which is used to transfer the clamping force from the top plate  55  of the clamping fixture  50  to the top surface of the SBC module  30 . Use of a controlled thickness spacer  54  prevents over-compression of the solder ball contacts  32  with the connecting pads  24 . The spacer  54  should also have an alignment feature  53  for fine alignment of the SBC module  30 . The fixture  40  should also have a stiffener  51  placed between the fastener  56  and the connecting article  60 . Use of a stiffener  51  prevents bowing of the connecting article  60 . 
     The same methods employed for enabling reliable connection to the SBC module are useable for connection to the connecting article when desired or necessary. FIG. 9 shows a modified interconnector  9  useable to connect with an article  65  having SBC type contacts  63  or other similar contacts. In this situation, a second alignment feature  57  could be used for aligning the interconnector article pads  64  with the connecting article solder balls  63 . A second spacer  56  could be used between the connecting article  65  and the enlarged first spacer  58 . The second spacer  56  could be made of an elastic polymer. 
     In a similar fashion, the alternate techniques described and shown in FIGS. 2-6 can be used for either or both contact sides of the interconnector  9 . The large pads  63  could be either of polymer or of a metallic material. A desirable process to fabricate large polymer pads  63  on the interconnector&#39;s article connecting surface is the following. A metallic sheet prestamped with a pattern having holes centered around, matching and larger than the article surface laser board arrangement is formed and attached to the interconnector surface. The patterned hole openings are filled partially or wholly with a polymer material. To form polymer pads, the structure is cured and the mask is removed either physically or by etching. To form metallic pads, the patterned holes are not filled wholly so as to leave room to spot or evaporate a desirable contact metallurgy over the laser ball and polymer surface before the mask is removed. 
     FIG. 10 shows the first step used to fabricate an interconnector assembly, such as the interconnector assembly  35  shown in FIG. 8, with conductive contact pads  24  for the fixture  40 . A substrate  11 , made of copper or other suitable conductive material, is fabricated with an area array of gold plated bottom surfaces  13  on the substrate bottom surface  12 , and a correspondingly positioned area array of gold plated top surfaces  15  on the substrate top surface  14 . Other noble metal such as Pt or Pd can be used for the substrate area array plating instead of gold. A barrier layer is typically used under the noble metal to prevent diffusion of the substrate to the surface. 
     FIG. 11 shows the next step of bonding the wire bonding contacts  16  of two bond wires  17 . The bond wire  17  is formed at an angle and cut to form a free standing structure with a straight end  18 . Although FIG. 11 shows two bonding wires  17  bonded to the gold plated top surface, the same process would be followed when bonding laser balls emanating from one, three or more bond wires to each gold plated top surface. 
     FIG. 12 shows the laser ball forming process at ends  18  of the angled bond wires  17  to create ball shaped contacts  19 . The size of a ball shaped contact  19  on the end of the angled bond wires  17  is controlled by the laser power density and the alignment of the focal point from the end  18  of the wire. The resulting array of angled bond wires  17  forms the first substrate sub-assembly  8  upon which a casting dam  20  is placed. 
     A casting dam  20  is placed around the array of angled bond wires as shown in FIG.  13 . The casting dam  20  is used to contain an uncured dielectric material  21  until it is cured. The dielectric is usually a liquid elastomer. A controlled volume of dielectric material  21  is dispensed into the cavity formed by the casting dam  20  such as to leave the ball shaped contacts  19  exposed. The dielectric material is allowed to settle out before curing. Once the dielectric has cured, the substrate  11  is chemically etched as shown in FIG.  14 . The etching process selectively removes the exposed unplated substrate on the substrate bottom surface  12  thereby leaving an array of individual conductive contact pads  24 . The resulting first interconnector assembly  35  is inverted as shown in FIG.  15 . The interconnector assembly  35  becomes an integral part of fixture  40 , as shown in FIG.  7 . 
     Any of the alternative methods described for forming high durability contacts on an interconnector  10  to connect to a module having solder ball contacts  32  can be used in producing a different interconnector assembly. Thus, FIG. 16 shows a second interconnector assembly  36  resulting when using polymer pads of the type illustrated in FIG.  5 . 
     A process to form the polymer pads includes the following steps. A conductive substrate, usually a copper substrate, is prestamped with the desired shape and dimensions. FIG. 17 shows such a typical substrate  70  in relation to a substrate carrier  71 . The stamping is such as to form a crater  72  in the substrate  70  at each point where it is desired to locate a polymer pad. An expanded view of the stamped substrate for a  13  by  11  pad array is shown in FIG.  18 . The substrate  70  is thus capable of having up to  143  pads. 
     FIG. 19 shows a magnified portion of a side view of the stamped substrate  70  with craters  72 . The craters  72  generally have fixed pitch and height. Wires  17 , having thermionic wire bonds  16  at one end, are put down at the bottom  74  of a crater  72  as shown in FIG.  19 . The wires are formed at an angle and cut to form a free standing structure with a straight end  18 . A laser ball  19  is formed at the straight end  18  of each wire. A polymer  76  is poured into each crater  72  so as to cover the wire bond  16 , but not to reach the top of the crater  77 . The polymer may be epoxy, polyimide or others known to those skilled in the art. The polymer is fully cured thereby forming a hard and large polymer pad. The resulting array of angled bond wires  17  forms the second substrate sub-assembly  75  upon which a casting dam  20  is placed. 
     The second interconnector  36 , shown in FIG. 16, can be formed by placing a casting dam  20  around the array of angled bond wires  17  of second substrate sub-assembly  75  in a similar fashion as was described for the embodiment shown in FIG.  13 . The casting dam  20 , shown inverted in FIG. 16, is used to contain an uncured dielectric material  21 , usually an elastomeric solution, until it is cured. A controlled volume of dielectric material  21  is dispensed into the cavity formed by the casting dam  20  such as to leave the ball shaped contacts  19  exposed. The dielectric material is allowed to settle out before curing. Once the dielectric has cured, the substrate  70  is chemically etched. The etching process is such as to selectively remove the substrate crater walls  78  so as to leave an array of individual metallic covered polymer pads  28 . The metallic cover  29  is generally plated with a noble metal. The plating serves as the contact interface with the solder ball  32  on an SBC module. The spaces  34  between contact pads  28  provides a means of mechanical decoupling from the adjacent contact pads and allows the contact pads  28  to compress independently for high compliance applications. The resulting second interconnector assembly  36  is inverted to the configuration shown in FIG.  16 . The second interconnector assembly  36  can become an integral part of fixture  40  replacing first interconnector  35  in FIG. 7, and an integral part of fixture  45  replacing first interconnector  35  in FIG.  8 . 
     FIG. 20 shows a third interconnector assembly  37  resulting when the technique shown in FIG. 6 is used. It uses plated wire bonding contacts  16  to connect directly with the solder ball connections. The wire bonding contacts  16  are captivated in a flexible polymer  26 . It is best to have the balls bonds  16  on the ends of the conductive wires  17  flush with the polymer top surface  29  of the thin layer of polymer  26  so as to provide a direct contact interface with the solder ball contacts of the SBC module. The third interconnector assembly  37  can be formed by using a thin, essentially flat substrate  80  shown in FIG.  21 . The substrate is marked correspondingly on both its flat surfaces to indicate the desired positions of the wire bonding contacts. Wires  17 , having thermionic wire bonds  16  at one end, are put down according to the substrate marking. The wires are formed at an angle and cut to form a free standing structure with a straight end  18 . A laser ball  19  is formed at the straight end  18  of each wire. The resulting array of angled bond wires  17  forms the third substrate sub-assembly  79  upon which a casting dam  20  is placed. 
     The third interconnector  37  shown in FIG. 20, is formed by placing a casting dam  20  around the array of angled bond wires  17 , contained in the third substrate sub-assembly  79 , in a similar fashion as was described for the embodiment shown in FIG.  13 . The casting dam  20 , shown inverted in FIG. 20, is used to receive a polymer  26  poured upon the substrate so as to enclose the wire bonding contacts  16 . The polymer may be epoxy, polyimide or others known to those skilled in the art. The polymer is fully cured thereby forming a thin polymer layer captivating the wire bonding contacts. A controlled volume of dielectric material  21  is dispensed into the cavity on top of the polymer layer  26  such as to leave the ball shaped contacts  19  exposed. The dielectric material, usually an elastomeric solution, is allowed to settle out before curing. Once the dielectric has cured, the substrate  62  is chemically etched. The etching process is such as to remove the substrate so as to leave an array of exposed individual, or groupings of, wire bonding contacts  16 . The wire bonding contacts  16  are generally plated with a noble metal. The plating serves as the contact interface with the solder ball  32  on an SBC module. Encasing the wire bonding contacts  16  in the thin layer of polymer  28  distributes the contact force from the solder balls  32  on the SBC module over a wider area on the top surface  27  of the interconnector socket  37  to prevent excessive deformation of the wire conductors  17  in the elastomer material  21 . The resulting third interconnector assembly  37  is inverted to the configuration shown in FIG.  17 . The third interconnector assembly  37  can become an integral part of fixture  40  replacing first interconnector  35  in FIG. 7, and an integral part of fixture  45  replacing first interconnector  35  in FIG.  8 . 
     While several embodiments of the invention have been described, it is understood to those skilled in the art, that many variations are available using the inventive structure and processes disclosed in this invention. It is also understood that although the inventive structures and processes were described variously using SBC contacts, wire bonding contacts, laser ball contacts and particular materials any other suitable contact technology or material may be used to achieve the intent and purpose of the present invention.