Abstract:
A socket for removably mounting an electronic device and which has utility for testing of the electronic device. The socket includes pinch-style support contacts which establish a reference seating plane for an IC package. The pinch-style support contacts each include a stationary contact arm, a movable contact arm, and a terminal portion. The stationary contact arm and the movable contact arm each include a contact surface configured to contact a terminal of the IC package. The stationary contact arm additionally includes an IC package support surface and extends beyond the height of the movable contact arm. A method of supporting and electrically connecting the socket and IC package is also disclosed.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a socket for removably mounting an electronic device. More specifically, the present invention relates to a pinch-style support contact configured to establish a reference seating plane for an integrated circuit (IC) package within the socket, as well as provide electrical communication for the IC package and the socket. 
   2. State of the Art 
   Testing a semiconductor die often involves establishing an electrical connection between testing equipment and the integrated circuitry of the die. Testing may be performed on an unpackaged semiconductor die that has been singulated from a semiconductor wafer, on a section of semiconductor dice that are still part of the wafer, or on all of the semiconductor dice on a wafer. Moreover, a bare semiconductor die that has undergone packaging may also be tested. One example of such a packaged semiconductor die is a so-called “flip-chip,” wherein discrete conductive elements, such as solder balls, are attached directly to or formed on the bond pads or redistributed bond pads at the ends of electrical traces formed on the active surface of the semiconductor die. The die is then “flipped,” or mounted face down, so that the solder balls may connect with contact members of another device, such as terminal pads of a carrier substrate. Another example is a “chip scale package,” which includes a die along with one or more package elements, such as encapsulating material in the form of thin protective coatings formed of a dielectric material bonded to the active surface, sides and back side of the semiconductor die; in addition, solder balls may be attached to or formed on ends of electrical traces on the active surface of the semiconductor die or directly to the semiconductor die&#39;s bond pads through openings in the encapsulating material. A Ball Grid Array (BGA) serves as yet another example that involves even more packaging: the semiconductor die is wire bonded to terminal pads on the top side of an interposer substrate and encapsulated, and solder balls are bonded to electrical traces on the bottom side of the substrate that are electrically connected to the terminal pads. 
   An electronic device to be tested will hereinafter be referred to as an integrated circuit package, or IC package, regardless of the singulation or packaging state of the semiconductor die or dice that form all or part of the IC package. One method of testing the IC package involves placing the IC package into a socket, which comprises a body with apertures that span through the body. These apertures house contact members that are aligned with electrical terminals of the IC package. For purposes of explanation only, it will be assumed that the terminals of the IC package are solder balls or other discrete conductive elements that protrude from the IC package. Often, the socket includes cover that, when closed, adjusts a slider to actuate arms of the contact members and engage the solder balls of the IC package. Contact members comprising arms which may open and close about solder balls may be referred to as pinch-style contacts. Once the IC package has been inserted, the socket may then be plugged into a printed circuit board (PCB) or other carrier substrate. 
   One example of a conventional socket with pinch-style contacts used in burn-in tests for electronic packages having BGA terminals is described in U.S. Pat. No. 6,350,138 issued to Atobe et al. (hereinafter “the &#39;138 patent”), on Feb. 26, 2002. The &#39;138 patent discloses, as shown in  FIG. 1A  and  FIG. 1B  hereof, a conventional socket  1  including a seating part  5   a  supporting a BGA package  9  on the periphery of the BGA package body. 
   The depicted socket  1  comprises a base  2  as the main socket body, a cover  3 , a slider  4  mounted on the base  2 , which serves as a contact part switching member, and an adaptor  5  mounted on the slider  4 . The base  2  may be attached to a PCB (not shown) for testing the BGA package  9 . The cover  3  is formed in the shape of a square frame with an opening at the center for the purpose of inserting the BGA package  9 . The base  2  and cover  3  are relatively movable toward and away from each other while maintaining a mutually parallel state. Contact members  6  are provided at positions which correspond to solder balls  11  provided on the lower side of the BGA package  9 . Each contact member  6  includes a pair of arms  6   a ,  6   b  for engaging a solderball  11 . The slider  4  includes a lattice-like partition wall capable of moving in a vertical direction, thus engaging the contact members  6 , causing the pair of arms of each contact member to open or close. A slider  4  capable of moving in a horizontal direction to engage the contact members  6  is also known in the art. The terminal portions  6   c  of the contact members  6  provide attachment to the PCB (not shown). 
   The contact members  6  pass through the base  2  and apertures  4   b  of the slider  4 . The contact arms  6   a ,  6   b  include tips  7 , located within substantially the same plane. The seating part  5   a  supporting the BGA package  9  creates a seating plane, the plane of a bottom surface  8  of the IC package body, or substrate  10 . One difficulty in the construction of the socket  1  is ensuring that the plane of the contact arm tips  7  is parallel to the seating plane. In addition, the spacing of the plane of the contact arm tips  7  must be a proper distance from the seating plane to ensure reliable electrical connection, as described further hereinbelow. The seating part  5   a  and the base  2  conventionally comprise plastic, and tolerances for forming plastic parts are typically high relative to the tolerances for the conventional stamping and stitching processes for forming contact members  6 . Tolerance stacking, or accumulation, of tolerances of a plurality of components may add to the error introduced by the individual tolerances. Nonplanarities in the seating part  5   a , as well as nonplanarities in the IC package substrate  10 , for example, bowing, may further contribute to error in the seating plane, and therefore error in the spacing between the seating plane and the plane of the contact arm tips  7 . 
   One example of a problem resulting from improper spacing between the plane of the contact arm tips  7  of a socket  1  and the seating plane of the BGA package  9  is that a trace (not shown) on a bottom surface  8  of the IC package substrate  10  may interfere with the movement of a contact arm  6   a ,  6   b  if the seating plane of the IC package is positioned too close to the plane of the contact arm tips  7 . The trace may protrude from the bottom surface  8  of the IC package substrate  10 . The contact arm tip  7  of a moving contact arm  6   a  or  6   b  may intersect the trace, preventing further movement, and therefore, contact with the solder ball  11 . If the contact member touches or rubs against the BGA package substrate  10 , especially while moving to make contact with the solder ball  11 , the bottom surface  8  of the IC package substrate  10  may be scratched, which may result in unreliability of the BGA package  9  in later service due to entry of moisture or other contaminants or undetected damage to circuitry, since scratches may damage the passivation layer on the IC package substrate  10 , or may expose the underlying traces and cause shorts. 
   Another problem with spacing error results from the contact arm tips  7  touching the BGA package  9 . The IC package substrate  10  may expand, for example during an increase in temperature, such as burn-in testing. Contact arm tips  7  touching the IC package substrate  10  when the IC package substrate  10  expands may move with the expansion of the IC package substrate  10 , causing the contact arms  6   a ,  6   b  to pull apart and lose reliable electrical communication with the solder ball  11 . 
   A third concern in relation to BGA package test sockets is that the IC package may not be held in the socket securely enough to maintain a valid testing process through sufficient continuous electrical communication between the socket and the IC package, yet not so securely held that the IC package or its electrical connections are damaged, particularly during removal of the IC package from the test socket. 
   In view of the foregoing, it appears that a socket with an improved seating plane for an IC package and a method of forming electrical connection with improved accuracy between a socket and an IC package would be useful. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention, in a number of exemplary embodiments, includes a socket employing a contact member in the form of a pinch-style support contact configured to establish a reference seating plane for an IC package within the socket as well as provide electrical communication between terminals of the IC package and the socket. By using an array of the pinch-style support contacts, the IC package may be securely held within the socket with increased accuracy in comparison to conventional sockets. As used herein, the term “terminal” includes any discrete conductive element protruding from an IC package, such as, without limitation, a solder ball, a metal ball, bump, pin or post, a conductive or conductor-filled polymer bump, stud or pillar, or a conductive-coated dielectric structure. 
   In accordance with one aspect of the present invention, a socket includes a plurality of pinch-style support contacts. Each pinch-style support contact comprises a stationary contact arm and a movable contact arm extending from a terminal portion. The stationary contact arm and the movable contact arm each include a contact surface configured to contact a terminal of the IC package. The terminal portion of each pinch-style support contact may be in electrical communication with the stationary contact arm and the movable contact arm, and configured for attachment to a PCB or other carrier substrate. The stationary contact arm includes an IC package support surface and extends distally beyond the height of the movable contact arm. 
   The socket may also include a slider or other actuation structure positioned and configured to movably, selectively engage each movable contact arm of the plurality of pinch-style support contacts to effect lateral movement thereof with respect to its associated, stationary contact arm. The contact surface of the movable contact arm may include, for example, a beak-like protrusion. The contact surface of the stationary contact arm may, for example, be substantially planar. The stationary contact arm and the movable contact arm may be configured for symmetrical or, alternatively, asymmetrical engagement with a terminal of the IC package. The movable contact arm and the stationary contact arm are fixed to the terminal portion, and at least the movable contact arm may, in one exemplary embodiment, be formed of a material resilient or elastic in bending to cause it to return toward a neutral, or unbiased, position when out of engagement with the slider or other actuation structure. 
   A socket according to the present invention may employ a plurality of pinch-style support contacts arranged in a two-dimensional array in a pattern and spacing or pitch mirrored to that of an array of terminals of an IC package. Another embodiment of a socket of the present invention also comprises an array of contact members, selected contact members being pinch-style support contacts of the present invention and the balance of the contact members comprising conventionally configured contact members. In either embodiment, the stationary contact arms of each pinch-style support may be configured to support an IC package and establish a reference seating plane. 
   Yet another embodiment of a socket of the present invention may employ a plurality of pinch-style support contacts arranged in a two-dimensional array in a pattern and spacing or pitch mirrored to that of an array of terminals of an IC package in addition to a supplemental plurality of pinch-style support contacts. The plurality of pinch-style contacts and the supplemental plurality of pinch-style contacts together form a two-dimensional array having dimensions greater than those of the array of terminals of the IC package. Alternatively, the plurality of pinch-style contacts and the supplemental plurality of pinch-style support contacts may be arranged in a two-dimensional array in a pattern and spacing or pitch mirrored to that of a plurality of arrays of terminals of a like plurality of IC packages. 
   One embodiment of a method according to the present invention of enabling electrical communication between an IC package and a socket having a plurality of pinch-style support contacts includes moving movable contact arms of the plurality of pinch-style support contacts away from their associated stationary contact arms, supporting the IC package on stationary contact arms of the plurality of pinch-style support contacts, and causing the movable contact arms to move toward their associated stationary contact arms to engage terminals of the IC package. Movable contact arms of the plurality of pinch-style support contacts may be resiliently biased toward the stationary contact arms to contact terminals of the IC package or positively moved toward the stationary contact arms. Electrical communication with the terminals is established through the stationary contact arm and the movable contact arm of the pinch-style support contacts. 
   Other features and advantages of the present invention will become apparent to those of skill in the art through consideration of the ensuing description, the accompanying drawings, and the appended claims. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     In the drawings, which illustrate what is currently considered to be the best mode for carrying out the invention: 
       FIG. 1A  is a cross-sectional view of a conventional socket; 
       FIG. 1B  is an enlarged portion of  FIG. 1A ; 
       FIG. 2  is a cross-sectional view of a schematic representation of a socket of the present invention and an engaged IC package; 
       FIG. 3A  is a front view of a schematic representation of a pair of contact arms of the present invention in an open position and a terminal of an IC package; 
       FIG. 3B  is a front view of a schematic representation of a pair of contact arms of the present invention in a closed position and a terminal of an IC package; 
       FIG. 4A  is a perspective view of a pair of contact arms of the present invention; 
       FIG. 4B  is a right-side view of the contact arms and terminal of  FIG. 3B ; 
       FIG. 4C  is a plan view of the contact arms and terminal of  FIG. 4B ; 
       FIG. 5A  is a perspective view of another embodiment of a pair of contact arms of the present invention and an engaged terminal of an IC package; 
       FIG. 5B  is a plan view of the contact arms and terminal of  FIG. 5A ; 
       FIG. 6A  is a top plan view of the contact arms of  FIG. 4C  arranged within a slider; 
       FIG. 6B  is a top plan view of the contact arms of  FIG. 5B  arranged within another slider; 
       FIGS. 7A–7D  are schematic representations of embodiments of pinch-style contacts of the present invention and a partial view of an IC package; and 
       FIG. 8  is a schematic representation of an array of contact members in a socket. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Generally, the present invention contemplates that a socket for removably mounting an IC package may include pinch-style support contacts which establish a reference seating plane for the IC package. A stationary arm of each pinch-style support contact may be used to support the IC package rather than the seating part of a conventional socket. Such a configuration may provide a socket with more consistent and reliable interconnect conditions. While the present invention is described herein in the context of a test socket, it is not so limited. 
   In accordance with one aspect of the present invention, as depicted in  FIG. 2 , a socket  100  is provided having pinch-style support contacts  110 . The pinch-style support contacts  110  may be formed of any suitable material, such as beryllium copper, copper alloy, phosphor bronze or any other conductive material suitable for contact members as known in the art. Each pinch-style support contact  110  includes a stationary contact arm  120 , a movable contact arm  130 , and a terminal portion  140  from which the stationary contact arm  120  and the movable contact arm  130  extend distally. As depicted and not by way of limitation, at least the movable contact arm  130  is cantilevered from terminal portion  140  and is formed from a conductive material resilient or elastic in bending, at least through a contemplated range of motion for movable contact arm  130 . The socket  100  is shown with a plurality of pinch-style support contacts  110  engaging an IC package  150  including terminals  160 . The terminals  160  are depicted as solder balls; however, the pinch-style support contacts of the present invention may be useful for engaging the terminals of any IC package wherein the terminals comprise discrete conductive elements, such as are employed in a flip-chip assembly, a pin grid array, or a ball grid array. 
   The stationary contact arm  120  and the movable contact arm  130  of socket  100  extend upwardly from a dielectric base member  105  thereof. The terminal portion  140  of each pinch-style support contact  110  may extend downwardly from the base member  105  to provide attachment for socket  100  to a PCB (not shown) or other carrier substrate. A slider  170  carried by the socket  100  may be used to initiate lateral movement of each movable contact arm  130  with respect to each stationary contact arm  120  to open and close each pinch-style support contact  110 . This enables an IC package to be removably mounted, that is, inserted, secured to and then removed from the socket  100 . The slider  170  may comprise a lattice-like partition wall mounted for movement in base member  105  in a horizontal or vertical direction. The movement of the slider  170  is conventionally actuated by an external force, for example, if a cover (not shown) of the socket  100  is pressed down. 
     FIG. 3A  depicts a movable contact arm  130  in an open position with respect to its associated stationary contact arm  120  for receiving a terminal  160  of the IC package  150 . A partition wall  170   a  (not shown) of the slider  170  may be moved in a first horizontal (with respect to socket  100 ) direction to engage with the movable contact arm  130  to actuate lateral movement thereof away from stationary contact arm  120 , resiliently biasing the movable contact arm  130  into the open position. The slider  170 , as shown, is movable in the horizontal direction to actuate this lateral movement. However, it is contemplated within the scope of the invention that a slider that is movable, for example upwardly, against a cam surface C of movable contact arm  130  in a vertical direction as shown in broken lines in  FIG. 3A  may be used to initiate the lateral movement. An engagement protrusion  115  which is to be selectively engaged with the slider  170  and which may include cam surface C may be provided on the movable contact arm  130 . 
   The movable contact arm  130  may be actuated to a closed position as depicted in  FIG. 3B  with respect to the stationary contact arm  120  by a horizontal movement of the slider  170  in the opposite horizontal direction, which as shown, permits resiliently biased movable contact arm  130  to move toward stationary contact arm  120 . Electrical communication is thus provided between the movable contact arm  130 , the stationary contact arm  120 , and terminal  160  of IC package  150 . This provides electrical communication between the socket  100  and the IC package  150  for testing. The IC package  150  may be removed by actuating the slider  170  once again to place the movable contact arm  130  in an open position. 
   The present invention may be implemented using a slider  170  and movable contact arm  130  cooperatively configured to open and close each pinch-style support contact  110  in a variety of ways. For example, as described above, the movable contact arm  130  may be elastically deformed to the open position and returned by its elastic property to the closed position. Conversely, the movable contact arm  130  may be elastically deformed by slider contact and movement to the closed position and returned by its elastic property to the open position. Alternatively, the movable contact arm  130  may be positively biased by contact with slider  170  to both the open and the closed position. In such an instance, the movable contact arm  130  need not be of a resilient or elastic material and may be hinged or otherwise configured to be pivotable at its proximal end with respect to terminal portion  140 . It is further understood that structure for effectuating lateral movement of the movable contact arm  130  need not be restricted to a horizontally or vertically movable slider. It is contemplated that any device configured for biasing the movable contact arm  130  may be employed in a socket of the present invention. For example, an eccentric cam placed proximate to movable contact arm  130  proximate a protrusion  115  and rotatable about a horizontal axis may be used to initiate movement of movable contact arm  130  toward and away from its associated stationary contact arm  120 . 
   Returning to  FIG. 2 , the stationary contact arm  120  may be configured to support the IC package  150  on a support surface  210   a  of a distal tip  210  thereof The distal tip  210  of the stationary contact arm  120  may protrude vertically a distance d above the movable contact arm  130  (see  FIG. 3B ). The distance dmay vary in different sockets  100  depending on the size of the terminals  160  to be engaged and, ideally, is the smallest distance possible which does not permit a distal tip of a movable contact arm  130  to drag on a surface of an IC package supported on stationary contact arm  120 , but still effectively clamp the smallest potential terminal  160 . Terminals  160 , which comprise solder balls having a 0.1 mm height, are preferably engaged by a movable contact arm  130  and a stationary contact arm  120  having a distal tip  210  protruding vertically a distance d of between about  30  and  50  microns above the distal end of movable contact arm  130 . The distance d may be greater in a socket  100  configured for engagement with an IC package having, for example, solder balls of an increased diameter. The socket  100  may include an array of the pinch-style support contacts  110 , and the distal tip  210  of each stationary contact arm  120  may support the IC package  150 , establishing a reference seating plane  230  for the IC package  150 . The geometry of the distal tip  210  of the stationary contact arm  120  may be configured to be non-intrusive to minimize the damage and/or inhibition of the performance of the IC package  150  from, for example, scratching of the surface. The distal tip  210  of the stationary contact arm  120  may be radiused, coined or chamfered at its edges or periphery to provide such a smooth, non-intrusive tip geometry, as shown in  FIG. 4A .  FIG. 4B  depicts the distal tip  210  in a right-side view of the stationary contact arm  120  of  FIG. 4A  and an engaged terminal  160  of an IC package  150 . 
   Returning again to  FIG. 3B , the stationary contact arm  120  includes a contact surface  220  configured to contact the terminal  160 . The contact surface  220  may be configured to provide sufficiently low Hertzian stress to minimize penetration into the terminal  160 , particularly during exposure to elevated temperatures, for example, during burn-in testing. “Burn-in” refers to the process of accelerating early-life failures. This is done by cycling a semiconductor die through a series of stresses at elevated temperature designed to simulate extreme field conditions in an attempt to cause failure of the die and provide a way to identify and remove from production those semiconductor dice which would have otherwise failed during early field use. A solder ball, particularly, may be softened at elevated temperatures, and the arms of a contact member may stick to the softened solder ball after the completion of the burn-in test, making it difficult to remove the IC package from the socket. The Hertzian stress formula may be useful for predicting local stresses and deformations at the point of contact depending on elastic properties, the size and shape of the contact zone, and relative position of the two bodies at the point of contact and the force pushing them together. The contact surface  220  depicted in  FIG. 3B  is a substantially planar surface, which is one example of a surface configured to provide sufficiently low Hertzian stress. 
   The movable contact arm  130  may have a beak-like protrusion  200  to concentrate stress against, and provide good contact with, the terminal  160 . The beak-like protrusion  200  may provide better contact by piercing any oxidation which may have formed on the surface of terminal  160 . Any bond with terminal  160  which may cause the beak-like protrusion  200  thereto will likely be broken when the movable contact arm  130  is pulled away from the terminal  160 . The slider  170  may be moved to engage the movable contact arm  130  to compel lateral movement thereof with respect to the stationary contact arm  130 , and the beak-like protrusion  200  located at the distal tip of the movable contact arm  130  may be pulled away in an arc. The resulting twisting motion may help break the bond between a beak-like protrusion  200  and a terminal  160 . The beak-like protrusion  200  may be located and oriented on movable contact arm  130  to contact the terminal  160  at the widest part of the terminal  160 , that is, the portion of the terminal  160  where the diameter becomes the largest relative to planes parallel to the bottom surface  240  of the IC package  150 . The beak-like protrusion  200  of the movable contact arm  130  is preferably positioned to contact the widest portion of a terminal  160  comprising a solder ball to avoid slippage of the movable contact arm  130  against the surface of terminal  160  or an unreliable contact therewith. 
   The nominal diameter or a range of diameters of the solder balls may be used to determine an optimum distance d, the difference in vertical protrusion of the stationary contact arm  120 , and therefore the reference seating plane, over the movable contact arm  130  in a socket  100 . An accurate reference seating plane may thus be useful to ensure that the solder balls are clamped at a desired location, for example, at the widest portion of each solder ball. 
   The stationary contact arm  120  and the movable contact arm  130  may be configured to symmetrically engage each terminal  160  of the IC package  150 , as depicted in the right side view of  FIG. 4B  and overhead view of  FIG. 4C . As shown, the symmetrical engagement may be effected diametrically across a terminal  160 . The stationary contact arm  120  and the movable contact arm  130  may be arranged on opposite sides of a partition wall  170   a  of the slider  170  as seen in  FIG. 6A . Each stationary contact arm  120  and its associated movable contact arm  130  of each pinch-style contact  110  are therefore arranged within separate but adjacent contact receiving apertures  170   c . Upon movement of the slider  170  in the direction indicated by arrowhead A, a movable contact arm  130  may be moved to the open position as shown in broken lines in  FIG. 6A  relative to the stationary contact arm  120 . 
   Alternatively, a stationary contact arm  120 ′ and its associated movable contact arm  130 ′ may be configured to asymmetrically engage a terminal  160 ′, as depicted in the plan side view  FIG. 5A  and overhead view  FIG. 5B . As illustrated, the asymmetric contact is effected by stationary contact arm  120 ′ and its associated movable contact arm  130 ′ at positions offset from a diameter of terminal  160 ′. The stationary contact arm  120 ′ and its associated movable contact arm  130 ′ may be arranged on opposite sides of the partition wall  170   a ′ of the slider  170 ′ as seen in  FIG. 6B . Upon movement of the slider  170 ′ in the direction indicated by arrowhead A, the movable contact arm  130 ′ is moved to the open position as shown in broken lines relative to the stationary contact arm  120 ′. The stationary contact arm  120 ′ and the movable contact arm  130 ′ may be positioned within diagonally opposing corners of the contact receiving aperture  170   c ′, resulting in the asymmetric engagement with the terminals  160 ′. 
   The present invention contemplates that there are many geometric configurations for the terminal portion  140  of the pinch-style support contact  110 , which may provide a point of attachment for the socket to a PCB or other carrier substrate (not shown). By way of example, and not to limit the scope of the present invention, as pictured in  FIG. 2 , a proximal segment  145  of the terminal portion  140  of the pinch-style support contact  110  may be positioned between the movable contact arm  130  and the stationary contact arm  120 . Alternatively, illustrated in  FIG. 7A , a terminal portion  141  of the pinch-style support contact  110  may comprise an extension of the movable contact arm  130  and a linking element  180  disposed between cantilevered stationary contact arm  120  and a medial portion of movable contact arm  130 . The linking element  180  may provide both electrical communication and mechanical connection between the stationary contact arm  120  and movable contact arm  130 .  FIG. 7B  illustrates another configuration for a linking element  180 ′ of a terminal portion  142 . As shown in  FIG. 7C , the terminal portion  143  of the pinch-style contact  110  may comprise an extension of the stationary contact arm  120  and a linking element  190  from which movable contact arm  130  is cantilevered. The linking element  190  may provide both electrical communication and mechanical connection between the stationary contact arm  120  and movable contact arm  130 .  FIG. 7D  illustrates another configuration for the linking element  190 ′ of the terminal portion  144  wherein terminal portion  144  may comprise an extension of stationary contact arm  120 . 
   A socket may comprise a plurality of contact members in an array in mirrored pattern and pitch to an array of terminals of an IC package and may be dimensioned such that each terminal thereof is discretely connected to the socket in electrical communication sufficient to test the IC package. Each of the contact members of a socket may comprise pinch-style support contacts  110  of the present invention, as shown in  FIG. 2 . The present invention also contemplates that a conventional socket may be refurbished, replacing a number of the conventional contact members comprising a pair of contact arms with pinch-style support contacts sufficient in a given arrangement to provide support for an IC package. Alternatively, a socket may be configured according to the present invention to employ both conventional contact members and support contacts of the present invention. In either instance, the stationary contact arms of the pinch-style support contacts of the present invention will extend above the upper ends of the conventional contact members to provide a reference plane for support of the IC package. As depicted in  FIG. 8 , a socket having an array  620  of contact members may have pinch-style support contacts  610  of the present invention positioned at the corners of the array  620 . The pinch-style support contacts  610  may thus be used to provide a reference seating plane for an IC package. Conventional contact members  605  may be used to complete the array of contact members. 
   In addition, it will be understood that while an array of 16 contact members, including four pinch-style support contacts  610  is shown in  FIG. 8 , the present invention includes within its scope sockets carrying any number of contact members, and any number of pinch-style support contacts according to the present invention employed therein in any suitable arrangement or pattern. For example, a socket of the present invention may include a plurality of pinch-style support contacts arranged in a two-dimensional array. A portion of the plurality of pinch-style support contacts may be arranged in a pattern and spacing or pitch mirrored to that of an array of terminals of a first IC package. The balance of the plurality of pinch-style support contacts comprise a supplemental plurality of pinch-style support contacts. The socket may therefore be used for testing a second IC package having an array of a greater number of terminals, without changes to the socket. Yet another embodiment of the socket of the present invention includes a plurality of pinch-style contacts arranged in a two-dimensional array in a pattern and spacing or pitch mirrored to that of a plurality of arrays of terminals of a like plurality of IC packages. The socket may therefore be used for simultaneously supporting a plurality of IC packages. 
   As will be appreciated by those of ordinary skill in the art, the present invention enables improved accuracy for forming electrical connection between a socket and an IC package. The features of the socket which are the most tightly controlled during socket manufacture, the contact arms, are used to establish a reference seating plane on which an IC package may be supported. The establishment of a reference seating plane provides accurate and sufficient vertical spacing or standoff between movable contact arms of the socket and the plane of the IC package. Accurate and sufficient vertical spacing or standoff removes the IC package from the potential for damaging shear contact with a movable contact arm which may compromise package integrity or electrical function, prevent damage to the IC package substrate and terminals, and provide more reliable electrical connection, thus overcoming previously experienced testing problems. 
   Although the foregoing description contains many specifics, these should not be construed as limiting the scope of the present invention, but merely as providing illustrations of some exemplary embodiments. Similarly, other embodiments of the invention may be devised which do not depart from the spirit or scope of the present invention. Features from different embodiments may be employed in combination. Moreover, the methods and devices described above are not limited to testing circumstances; rather, they could also be used for interconnect devices in permanent or semipermanent packaging. The scope of the invention is, therefore, indicated and limited only by the appended claims and their legal equivalents, rather than by the foregoing description. All additions, deletions, and modifications to the invention, as disclosed herein, which fall within the meaning and scope of the claims are to be embraced thereby.