Abstract:
An interconnection device is provided for temporary connection of a first electronic system to a second electronic system having a support substrate that includes an ordered array of conductive solder pads. A plurality of coil signal contacts are mounted to the conductive solder pads. Each one of the coil signal contacts comprises a central longitudinal axis, a top turn and a bottom turn that are arranged in spaced relation to one another. In this way, the bottom turn of one of the plurality of coil signal contacts is fastened to each of the conductive pads such that the top turns are spaced away from the support substrate.

Description:
This application is a continuation application of U.S. application Ser. No. 10/100,667, filed on Mar. 18, 2002 now U.S. Pat. No. 6,551,112. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to techniques and assemblies for making electrical interconnections to contact elements on a semiconductor device during a temporary connection to the device, i.e. in test and/or burn-in procedures. 
     BACKGROUND OF THE INVENTION 
     Rapid advances in microelectronic devices are continuously demanding finer pitch connections between electronic chip carriers and printed circuit boards (on the order of a few hundred micrometer pitch or less). This demand as well as the demand for low cost electronic packages have led to the increased use of surface mount technology (SMT) over the conventional plated-through-hole (PTH) technology in the recent years. At present, more than two thirds of integrated circuits (IC) including both memory and logic devices are assembled by SMT. SMT packages commonly found in a printed circuit board (PCB) assembly are leaded chip carriers such as small outline integrated circuits (SOIC), plastic leaded chip carrier (PLCC), quad flat pack (QFP), thin small outline package (TSOP), or tape carrier package (TCP). These leaded chip carriers depend upon a perimeter connection between an IC package and a PCB. The perimeter connection scheme of SMT packages has reached its limitation in terms of connection pitch and I/O capability, particularly for high performance IC&#39;s. 
     To relieve the limitations of perimeter connections and thereby to increase the packaging density, area array connection and packaging schemes have become popular. Some of the area array packages developed for SMT include the ball grid array (BGA) package, solder column grid array (SCGA), direct chip attach (DCA) to PCB by flip chip connection, tape ball grid array (TBGA), and chip scale packages (CSP). A typical BGA array has a pitch in the 40-50 mil range, while for the CSP arrays the pitch may go down to 15 mils. Among them, BGA is currently the most popular one, where solder balls connect a module carrying an IC to a PCB. This technology is an extension of the controlled collapse chip connection (C4) scheme originally developed for solder bump connection of multiple chips to a ceramic substrate. 
     The IC on the module can be connected to the module in several ways as taught by Mulles et al., U.S. Pat. No. 5,241,133; Massingill, U.S. Pat. No. 5,420,460; and Marrs et al., U.S. Pat. No. 5,355,283 among others. Ceramic or organic module substrates can be employed depending on the performance, weight and other requirements. The common feature, however, is that the connection between the IC carrier and the next level PCB is accomplished by an array of solder balls which are attached to the module by a solder alloy with a lower melting temperature. 
     Semiconductor components, such as bare dice, or chip scale and BGA packages, must be tested prior to shipment by semiconductor manufacturers. Since these components are relatively small and fragile, carriers have been developed for handling the components for testing. The carriers permit electrical connections to be made between external contacts on the components, and testing equipment such as burn-in boards. On bare dice, the external contacts typically comprise planar or bumped bond pads. On chip scale packages, the external contacts typically comprise solder balls in a dense array, such as a ball grid array, or a fine ball grid array. 
     A significant problem associated with BGA modules is the difficulty associated with testing and “burning-in” the assembly after a silicon die has been assembled on them. Although the die may have been tested prior to BGA assembly, the devices and circuitry have to be retested because of the additional temperature and handling exposures involved in the BGA and other assembly procedures. This poses a problem because the only way to access the chip devices is through the BGA balls. Establishing reliable contact for testing and burn-in has been difficult when using prior art testing and burn-in devices that are often designed for engaging pin grid array modules. Even if alternate means could be designed to contact the BGA balls, these would most likely require mechanical pressure of pads or “bed-of-nails” type pin arrays on a test board to be pressed against the solder balls. These approaches are often unreliable due to the softness of the BGA balls and the tenacious oxide present on their surface. Additionally, the application of pressure during the testing can deform or even dislodge the BGA balls causing yield loss. 
     What is needed is an interconnect component that includes contacts that make a temporary non-damaging electrical connection with the external BGA contacts. The interconnect component should provide power, ground and signal paths to the BGA component. A biasing force for biasing the component against the interconnect must be provided that will achieve viable electrical connection, but without damaging the delicate solder ball surfaces. 
     SUMMARY OF THE INVENTION 
     The present invention provides an interconnection device for temporary connection of a first electronic system to a second electronic system having a support substrate that includes an ordered array of conductive solder pads. A plurality of coil signal contacts are mounted to the conductive solder pads. Each one of the coil signal contacts comprises a central longitudinal axis, a top turn and a bottom turn that are arranged in spaced relation to one another. In this way, the bottom turn of one of the plurality of coil signal contacts is fastened to each of the conductive pads such that the top turns are spaced away from the support substrate. 
     In one alternative embodiment of the invention, an interconnection device for temporary connection of a first electronic system to a second electronic system is provided having a plurality of dual coil signal contacts where each one of the dual coil signal contacts comprises a tail connecting a top coil having a contact turn and a bottom coil having a contact turn. Each of the dual coil contacts is arranged such that the top coil and the bottom coil project outwardly and away from one another. The dual coil contacts are mounted within a support substrate having a top carrier including a first plurality of through-holes, a bottom carrier including a second plurality of through-holes, and a lock-plate including a third plurality of through-holes. The top carrier and the bottom carrier are joined to one another such that the first plurality of through-holes and the second plurality of through-holes are substantially coaxially aligned, and the lock-plate is slideably sandwiched between the top carrier and the bottom carrier. In this way, the lock-plate may slide between (i) a first position wherein the first plurality of through-holes, the second plurality of through-holes, and the third plurality of through-holes are coaxially aligned whereby one of the dual coil signal contacts may be slid through the through-holes so as to be mounted to the substrate; and (ii) a second position wherein only the first plurality of through-holes and the second plurality of through-holes are coaxially aligned and the tail of the dual coil contact is locked within the third through-hole. 
     In another alternative embodiment of the invention, an interconnection device for temporary connection of a first electronic system to a second electronic system is provided including a plurality of dual coil signal contacts. Each of the of dual coil signal contacts comprises a top coil having a contact turn, a bottom coil having a contact turn, and a central lock-turn that has a substantially larger diameter than the contact turns. Each of the dual coil contacts are arranged such that the top coil and the bottom coil project outwardly and away from the lock-turn. The dual coil signal contacts are mounted within a support substrate having a top carrier including a plurality of through-holes and a bottom carrier including a plurality of countersunk through-holes. The countersunk through-holes are defined by an annular ledge disposed about a central opening of the through-hole. When a dual coil signal contact is positioned within the bottom carrier of a substrate such that its bottom coil projects outwardly from the countersunk through-hole, the central lock-turn engages the ledge and is locked in place when the top carrier and the bottom carrier are joined to one another. 
     An electrical connection system is also provided in which a temporary connection is made between an electronic circuit package and an electronic system. In this aspect of the invention, a semiconductor package is provided having a housing with a plurality of solder balls arranged in an array on at least one side. Each of the solder balls comprises a semispherical profile having a center top region spaced away from the housing, and a peripheral edge region that is between the center top region and the housing. An interconnection device is provided having a support substrate including an ordered array of conductive pads. Each one of the signal contacts comprises a central longitudinal axis, a top conductor and a bottom conductor that are arranged in spaced relation to one another. The top conductor is sized so as to engage the substantially semispherical solder ball along the peripheral edge region, and the bottom conductor is fastened to one of the conductive pads. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features and advantages of the present invention will be more fully disclosed in, or rendered obvious by, the following detailed description of the preferred embodiment of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts and further wherein: 
     FIG. 1 is a perspective view of a surface mount technology chip carrier positioned above a test and burn-in connector formed in accordance with the present invention; 
     FIG. 2 is a partially broken away, cross-sectional view of the test and burn-in connector shown in FIG. 1, as taken through an arbitrary section of the device; 
     FIG. 3 is a cross-sectional view similar to that shown in FIG. 2, illustrating an alternative embodiment of the present invention; 
     FIG. 4 is a cross-sectional view of the test and burn-in connector of the present invention, similar to FIGS. 2 and 3, showing a through-hole mountable signal contact embodiment of the present invention. 
     FIG. 5 is a broken-away view, partially in phantom, of the test and burn-in connector of the present invention, showing a signal contact mounted to a solder pad of a substrate and having a top, contact turn just prior to engagement with a solder ball of a surface mount technology ball grid array chip carrier package; 
     FIG. 6 is a front elevational view, partially in phantom, of an alternative embodiment of the signal contact shown in FIG. 5; 
     FIG. 7 is a front elevational view, similar to FIG. 5, showing a conductive cap arranged on a signal contact in accordance with a further embodiment of the present invention; 
     FIG. 8 is a front elevational view of a dual coil signal contact; 
     FIGS. 9 and 10 are side cross-sectional views of an alternative embodiment of test and burn-in connector utilizing the dual coil signal contact shown in FIG. 8; 
     FIG. 11 is an alternative embodiment of substrate comprising a dual coil signal contact having a lock turn; 
     FIG. 12 is a cross-sectional view of an alternative embodiment of the test and burn-in connector of the present invention shown in FIG. 1, as taken through an arbitrary section of the device, illustrating a tapered coil signal contact; and 
     FIG. 13 is a side cross-sectional view of a test and burn-in connector similar to FIG. 12, showing a reverse taper signal contact. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     This description of preferred embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. The drawing figures are not necessarily to scale and certain features of the invention may be shown exaggerated in scale or in somewhat schematic form in the interest of clarity and conciseness. In the description, relative terms such as “horizontal,” “vertical,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing figure under discussion. These relative terms are for convenience of description and normally are not intended to require a particular orientation. Terms including “inwardly” versus “outwardly,” “longitudinal” versus “lateral” and the like are to be interpreted relative to one another or relative to an axis of elongation, or an axis or center of rotation, as appropriate. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. The term “operatively connected” is such an attachment, coupling or connection that allows the pertinent structures to operate as intended by virtue of that relationship. In the claims, means-plus-function clauses are intended to cover the structures described, suggested, or rendered obvious by the written description or drawings for performing the recited function, including not only structural equivalents but also equivalent structures. 
     Referring to FIGS. 1 and 2, a burn-in or test carrier  1  comprises a substrate  4  having a plurality of resilient signal contacts  8  mounted on at least one side. Substrate  4  may be formed from any of the well known dielectric, polymer materials that are suitable for injection molding, and are commonly used in the connector or semiconductor packaging industry, e.g., polyhalo-olefins, polyamides, polyolefins, polystyrenes, polyvinyls, polyacrylates, polymethacrylates, polyesters, polydienes, polyoxides, polyamides and polysulfides and their blends, co-polymers and substituted derivatives thereof. Substrate  4  is generally planer, and may include multiple layers of circuit traces  5  or the like (FIGS. 2 and 3) to facilitate interconnection with a test system (not shown). Also, substrate  4  may include multiple moving parts adapted for releasably locking signal contacts  8  in place, as will hereinafter be disclosed in further detail. 
     A plurality of solder pads  6  may be formed on one or both sides of substrate  4 , so that signal contacts  8  may be surface mounted on one or both sides of substrate  4  (FIGS.  2  and  3 ). Alternatively, plated-through-holes (PTH)  7  may be defined through substrate  4  for mounting of signal contacts  8  (FIG.  4 ). Solder pads  6  or PTH  7  are typically in electrical communication with circuit traces  5  so as to complete the required electrical circuits. 
     Referring to FIGS. 5-7, signal contacts  8  preferably comprise coiled or helical conductors, that are formed from copper alloys or spring steels. Signal contacts  8  include multiple turns  9  that are disposed about a central longitudinal axis  12 , and include a top turn  14  having a free end  17 , and a bottom turn  18  having a tail  19 . In some embodiments, signal contacts  8  may have a highly conductive tape or soft wire conductor  21  (e.g., gold) wound around one or more turns  9  to enhance electrical engagement with solder ball contacts  20  on a ball grid array (BGA)  22  (FIG.  6 ). Of course, other area array packages, e.g., solder column grid arrays and tape ball grid arrays, as well as direct chip attach, flip chip connection packaging, chip scale packages, and circuit board contact pads may all be temporarily electrically and mechanically engaged with signal contacts  8 . 
     It is important that no portion of top turn  14  gouge or scratch the surface of solder ball contact  20  during engagement, since this will cause reliability and manufacturing problems during subsequent steps of the manufacturing process. Thus in one embodiment, free end  17  is turned downwardly, or inwardly toward central longitudinal axis  12  of signal contact  8  (FIG.  5 ). Top turn  14  is preferably arranged so as to be substantially perpendicular to central longitudinal axis  12  thereby providing for a distributed chordal contact with the outer surface of solder ball contact  20 . Top turn  14  comprises a diameter that is sized so that a substantially semispherical solder ball contact  20  is engaged along the peripheral edge region  27  that is spaced away from the center top region  30  of semispherical solder ball  20  (FIG.  5 ). In this way, any scratches that are caused during engagement between signal contacts  8  and solder ball  20 , reside in a region that is far from the location of final engagement and soldering of solder ball contact  20 . Alternatively, a conductive cap  35  may also be mounted on top turn  14  to further enhance the mechanical and electrical engagement between signal contact  8  and solder ball  20  (FIG.  7 ). 
     Bottom turn  18  may be formed so as to be substantially parallel to top turn  14  for surface soldering to solder pads  6  on substrate  4  or, tail  19  may project outwardly from bottom turn  18  for insertion into a PTH  7  in substrate  4  (FIGS.  4  and  5 ). In addition, a dual signal contact  38  may be formed by joining the tails  19  of two signal contacts so as to form a lock-in tail  40  between the them (FIG.  8 ). Dual signal contact  38  is mounted within a substrate  41  that comprises a top carrier  42 , a bottom carrier  44 , and a lock-plate  46  that is slideably sandwiched between top carrier  42  and bottom carrier  44  (FIGS.  9  and  10 ). Substrate  41 , like substrate  4 , may be formed from any of the well known dielectric, polymer materials that are suitable for injection molding, and are commonly used in the connector or semiconductor packaging industry, e.g., polyhalo-olefins, polyamides, polyolefins, polystyrenes, polyvinyls, polyacrylates, polymethacrylates, polyesters, polydienes, polyoxides, polyamides and polysulfides and their blends, co-polymers and substituted derivatives thereof. 
     Top carrier  42  and bottom carrier  44  define a plurality of through-holes  47 . Top carrier  42  and bottom carrier  44  are assembled to one another such that through-holes  47  are arranged in coaxially aligned relation to one another. Lock-plate  46  is generally planar, and comprises a plurality of elongate through-holes  50 , i.e., through-holes that are rectangular or are defined by spaced-apart major and minor axes so as to be oval in shape. To assemble substrate  41 , top carrier  42  and bottom carrier  44  are fastened to one another such that lock-plate  46  is slideably received between them, and through-holes  47  and through-holes  50  are arranged in coaxially aligned relation to one another. Once in this position, dual signal contacts  38  are positioned within through-holes  47  and through-holes  50  in substrate  41  (FIG.  9 ). With dual signal contacts  38  positioned within through-holes  47  and through-holes  50 , lock plate  46  is slid relative to top carrier  42  and bottom carrier  44  so that through-holes  50  move relative to through-holes  47  thereby positioning a portion  49  of lock-plate  46  adjacent to lock-in tail  40  of dual contacts  38 . Dual signal contacts  38  may be released by reversing the foregoing process. 
     In a further embodiment of the present invention, bottom carrier  44  includes a counter-sink hole  52  formed at the top of through-hole  47  that is defined by a countersink ledge  53  annularly disposed about the central opening of through-hole  47 . A dual signal contact  55  is formed substantially like dual signal contact  38 , except that a larger diameter turn  57  is positioned between the coils of the signal contacts. Signal contact  55  is assembled to bottom carrier  44  by inserting a coil through through-hole  47  until turn  57  engages ledge  53  of counter-sink  52 . Once in this position, top carrier  42  is assembled over bottom carrier  44  such that the remaining coils project through through-holes  47 . Top carrier  42  is then securely fastened to bottom carrier  44 . 
     Signal contacts  8  may also be shaped so as to control their effective spring rate. For example, a signal contact  80  may comprise turns  83  of varying diameter, such as would yield a tapered outer profile. In addition, top turn  86  may have a smaller or larger diameter than bottom turn  87  so that signal contact  80  may taper upwardly or downwardly as required. 
     It is to be understood that the present invention is by no means limited only to the particular constructions herein disclosed and shown in the drawings, but also comprises any modifications or equivalents within the scope of the claims.