Abstract:
An interconnection device for interconnecting a number of first terminals to a number of second terminals. The interconnection device includes a conductive housing and a number of contacts that are insulated from the conductive housing. This configuration may provide shielding to the number of contacts from outside sources of electro-magnetic interference. Further, a number of conductive ribs may be provided between adjacent contacts, thereby shielding the contacts from cross-talk interference between adjacent contacts. Finally, the impedance of each contact in the interconnection device may be controlled to provide a stable bandpass, and may be programmable to match, or correct for, the input impedance of a corresponding device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a regular application filed under 35 U.S.C. § 111(a) claiming priority, under 35 U.S.C. § 119(e)(1), of provisional application Ser. No. 60/000,942, previously filed Jul. 7, 1995 under 35 U.S.C. § 111(b). 
    
    
     TECHNICAL FIELD 
     The present invention deals broadly with the field of devices for interconnecting electrical contacts. More narrowly, however, the invention is related to technology for inter-connecting a plurality of corresponding terminals by means of an electrical conductor between an integrated circuit device and a printed circuit board or between two printed circuit boards. The device is particularly useful for interfacing an integrated circuit with a tester, including a printed circuit board, during the manufacturing process to assure operativeness. The preferred embodiments of the present invention are directed to means for controlling the impedance and/or providing shielding to the interconnection between devices. 
     BACKGROUND OF THE INVENTION 
     Devices and methods for effecting electrical interconnection between two conductors are generally known. A specialized area of such interconnection has been recently expanding with the advent of integrated circuit technology. For example, in the manufacturing process for fabricating integrated circuit devices, each integrated circuit must be tested for operativeness. Thus, each lead of an integrated circuit device must be interconnected with a tester apparatus, wherein the tester apparatus may determine the functionality and performance of the corresponding integrated circuit device. 
     During such testing, an integrated circuit device is typically placed into an interconnect device (such as a test socket). The interconnect device interconnects each lead of the integrated circuit with a corresponding terminal of a printed circuit board. This may be accomplished with a number of contacts within the interconnect device. A tester apparatus is then electrically coupled to the printed circuit board such that the signals provided to each lead of the integrated circuit may be controlled and/or observed by the tester apparatus. 
     A further specialized area of interconnecting electrical contacts focuses on the interconnection of two printed circuit boards. These interconnections have applications utilizing insertable boards, such as memory cards, or multi-chip boards which are highly miniaturized and integrated. 
     Several technologies for packaging an integrated circuit chip into an semi-conductor package have been developed. These may be generally categorized as pin grid array (PGA) systems and leaded semi-conductor devices. The leaded semi-conductor devices include plastic leaded chip carriers (PLCC), dual in-line packages (DIP) and Quad Flat Pack (QFP). Each packaging type requires a particular array of leads to be interconnected with a printed circuit board. 
     A number of methods for connecting integrated circuits, such as PGA devices, with a printed circuit board are known. It is believed that limitations to these systems are the contact length and the usual requirement of mounting the contacts in through-holes located in a printed circuit board. The contact and through-hole mounting limits the mounting speed of the semi-conductor device while inducing discontinuities and impedance which cause signal reflections back to the source. Further, the design causes high lead inductance and thus problems with power decoupling and may result in cross-talk with closely adjacent signal lines. 
     Johnson recently disclosed in U.S. Pat. No. 5,069,629 (issued Dec. 3, 1991) and U.S. Pat. No. 5,207,584 (issued May 4, 1993) electrical interconnect contact systems which are directed to addressing both mechanical and electrical considerations of such systems. The disclosure of these references is incorporated herein by reference. 
     The disclosures of Johnson are directed to an interconnect device which comprises a generally planar contact which is received within one or more slots of a housing. In one embodiment, each contact is of a generally S-shaped design and supported at two locations (the hook portions of the S) by a rigid first element and an elastomeric second element. As disclosed, the Johnson electrical interconnect provides a wiping action which enables a good interface to be accomplished between the contact and the lead of the integrated circuit, and between the contact and terminals on a printed circuit board. Further, Johnson discloses an electrical contact that can sustain high operating speeds, and provides a very short path of connection. Such a contact may have low inductance and low resistance, thereby minimizing the impedance of the contact. 
     In recent years, the number of leads which may extend from one of the above referenced semi-conductor packages has substantially increased. Integrated circuit technology has allowed the integration of several complex circuits onto a single integrated circuit. Often, hundreds of thousands of gates may be incorporated into a single chip. A consequence of such integration is often a requirement that many input/output leads must extend from a corresponding semi-conductor package. To limit the overall dimensions of the semi-conductor package, the spacing between leads of many of the above referenced semi-conductor packages has decreased. As a result thereof, the spacing between the contacts of a corresponding interconnect device has also decreased. 
     The decrease in spacing between contacts of an interconnect device has necessarily increased the capacitance therebetween. Thus, a signal on a first contact of an interconnect device may affect the signal on a second contact of the interconnect device. This phenomenon is known as cross-talk. Cross-talk increases the noise on a contact, and thus adversely affects the reliability of the interconnect system. 
     Electromagnetic Interference (EMI) is another source of noise which reduces the reliability of interconnect systems. Typically, a low background level of EMI is present in the environment. Other, more obtrusive sources of EMI included IC testers, computers, test equipment, cellular phones, television and radio signals, etc. All of these sources of EMI should be considered when testing higher performance integrated circuits. 
     Another consideration of interconnect devices is the impedance provided by the corresponding contacts. It is recognized that the interconnect path between, for example, a semi-conductor package lead and a terminal on a printed circuit board, should have a relatively high and stable bandwidth across all applicable frequencies. That is, not only should the impedance of the interconnect system be minimized as disclosed in Johnson, but the impedance should also be controlled such that a relatively flat bandpass over all applicable frequencies exists. 
     To achieve a stable bandpass, it is often important to have a contact which provides impedance matching between a corresponding input of an integrated circuit and the corresponding driver. For example, if a tester is driving an input of an integrated circuit device via an interconnect device, it may be important for the interconnect device to provide an impedance such that the impedance of the driver matches the input impedance of the integrated circuit. Since the input impedance of the integrated circuit is often fixed, the impedance of the interconnect device may be used to correct for any impedance mismatch between the driver and the integrated circuit. Impedance matching may be important to minimize reflections and other noise mechanisms which may reduce the reliability and accuracy of the corresponding system. 
     Accordingly, a need exists for an improved electrical interconnect system to be utilized for interconnecting integrated circuit devices with printed circuit boards or for interconnecting multiple printed circuit boards. The interconnecting device should provide shielding for both cross-talk and EMI. The interconnect device should also allow the user to control and/or select the impedance for each contact provided therein. 
     SUMMARY OF THE INVENTION 
     The present invention addresses these needs as well as other problems associated with prior art electrical interconnect systems. The present invention provides an interconnect system whereby a number of contacts are shielded from outside sources of electro-magnetic interference by a conductive housing. Further, each of the contacts may be shielded from cross-talk interference between adjacent contacts by conductive ribs extending therebetween. Finally, the impedance of each contact in the interconnect system may be controlled to provide a stable bandpass, and the impedance may be programmable to match, or correct for, the input impedance of a corresponding device. 
     In an illustrative embodiment, the present invention provides an electrical interconnect between a number of first terminals and a number of second terminals. The present invention may include a housing, a number of contacts, and a number of insulating elements. Both the housing and the contacts are preferable made from a conductive material. The insulating elements may insulate the number of contacts from the housing. By providing an electrically conductive housing, the contacts may be shielded from outside sources of EMI. At the same time, however, because the contacts are electrically isolated from the housing, the contacts may maintain an independent interconnection between the number of first terminals and the number of second terminals. 
     An addition advantage of the present invention is that the impedance seen by the contacts is stabilized and controllable. In the present invention, a controlled impedance is created between the contacts and the conductive housing. By varying the geometry of the contacts and the insulating element, the impedance between the contacts and the housing can be programmed. This may provide a stable, and controllable, bandpass for the signals passing through the interconnection system. 
     In addition to the above, the present invention contemplates shielding the upper and lower portions of the contacts that extend above and/or below the conductive housing. It is contemplated that this may be accomplished in a number of ways, including providing a conductive skirt or gasket that is electrically coupled to the housing, and may extend toward the first and/or second terminals. The conductive skirt may shield the upper and/or lower portions of the contacts from electro-magnetic interference from outside sources. In addition, and to shield each of the contacts from cross-talk interference from adjacent contacts, it is contemplated that a number of ribs may be electrically coupled to the housing and may extend between adjacent contact. Selected ones of the number of ribs may extend above and/or below the top and/or bottom surfaces of the housing. The rib extensions may shield the top and/or bottom portions of the contacts from cross-talk interference. Further, when the first or second terminal is a device lead, the rib extensions may shield cross-talk interference between adjacent device leads, and between the device leads and adjacent contacts. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, in which like reference numerals indicate corresponding parts or elements of preferred embodiments of the present invention throughout the several views: 
     FIG. 1 is a fragmentary perspective view showing a conductor between two parallel plates; 
     FIG. 2 is a perspective view with some parts cut away showing a first embodiment of the present invention in combination with an integrated circuit and a printed circuit board; 
     FIG. 3 is a perspective view showing a housing in accordance with the first embodiment of the present invention; 
     FIG. 4 is a perspective view with some parts cut away showing a second embodiment of the present invention in combination with a printed circuit board; 
     FIG. 5 is a perspective view with some parts cut away showing a third embodiment of the present invention in combination with a printed circuit board; 
     FIG. 6 is a perspective view showing a housing in accordance with the fourth embodiment of the present invention; 
     FIG. 7 is a side elevational view showing a housing in accordance with the first embodiment of the present invention with a wire mesh placed over the top surface thereof; 
     FIG. 8A is a perspective view of an S-shaped contact as used in the present invention; 
     FIG. 8B is a perspective view of an S-shaped contact as used in the present invention with a predetermined portion removed therefrom; 
     FIG. 8C is a perspective view of an S-shaped contact as used in the present invention with a number of predetermined portions removed therefrom; 
     FIG. 9A is a perspective view of a sleeve as used in the first embodiment of the present invention with a predetermined portion removed therefrom; 
     FIG. 9B is a perspective view of a sleeve as used in the first embodiment of the present invention with a number of predetermined portion removed therefrom; and 
     FIG. 10 is a perspective view showing a housing in accordance with the first embodiment of the present invention, wherein a number of S-shaped contacts having varying impedance characteristics are preselected and placed within corresponding slots within the housing. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Detailed embodiments of the present invention are disclosed herein. However, it is to be understood that the disclosed embodiments are merely exemplary of the present invention which may be embodied in various systems. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one of skill in the art to variously practice the invention. 
     FIG. 1 is a fragmentary perspective view showing a conductor between two parallel plates. The diagram is generally shown at  10 . FIG. 1 generally shows the relationship between the physical characteristics of an electrical contact structure and the resulting impedance. A first plate  12  and a second plate  14  are shown extending substantially parallel to one another. A center plate  16  is disposed therebetween, wherein a dielectric or insulating material  18  is provided between the center plate  16  and the first and second plates  12 , and  14 . 
     For purposes of this discussion, it is assumed that center plate  16  is centered between first plate  12  and second plate  14 . Thus, center plate  16  is positioned a distance “D” from first plate  12  and a same distance “D” from second plate  14 . Center plate  16  has a length of “L” and a width of “W” as shown. Center plate  16 , thus, has an area equal to “W” times “L”. The capacitance between center plate  16  and first plate  12  is generally given by the formula: 
     
       
         
           C=ε·A/D  
         
       
     
     wherein A is the area of center plate  16 , D is the distance between center plate  16  and first plate  12 , and ε is the permittivity of dielectric  18 . A similar formula can be found for the capacitance between center plate  16  and second plate  14 . The corresponding impedance is generally expressed by the formula: 
     
       
           Z= 1/(2 πfC )  
       
     
     where f is the frequency. 
     It can readily be seen that the impedance can be affected by varying the area of center plate  16 , the distance between center plate  16  and first plate  12  and/or second plate  14 , and the permittivity of dielectric material  18 . 
     FIG. 2 is a perspective view with some parts cut away showing a first embodiment of the present invention in combination with an integrated circuit  32  and a printed circuit board  34 . The drawing is generally shown at  30 . Integrated circuit  32  has a lead  38  which may electrically engage an S-shaped contact element  40 . A lower portion (not shown) of S-shaped contact element  40  may electrically engage a terminal  42  of printed circuit board  34 . The S-shaped contact element  40  is disposed within a slot within a housing  36 . The construction of the S-shaped contact and the corresponding housing assembly  36  are described in U.S. Pat. No. 5,069,629, issued to Johnson on Dec. 3, 1991, which is incorporated herein by reference. Although not specifically shown, it is contemplated that any size, shape or type of contact element may be used in conjunction with the present invention. This includes both rigid planer contact elements, deformable contact elements, or any other type of contact elements. 
     In the first embodiment of the present invention, housing  36  is manufactured from a conductive material such as aluminum. It is recognized, however, that housing  36  may be made from any conductive material. Housing  36  has a number of slots disposed therein, thereby forming a number of ribs therebetween. One such rib is shown at  44 . In a preferred embodiment, the aluminum housing is manufactured from an aluminum blank. Each of the number of slots may be formed using an electro-discharge machining (EDM) process or a laser cutting process. 
     A sleeve  46  may be disposed in predetermined ones of the slots of housing  36 . Each sleeve  46  may be manufactured from a dielectric or insulating material such as polytetrafluoroethylene. Polytetrafluoroethylene is sold under the registered trademark “TEFLON®” by Dupont Corporation. It is recognized, however, that any insulating material may be used to achieve the benefits of the present invention. It is further recognized that a user may select an insulating material which has a desired permittivity value, thereby providing the desired impedance characteristics to a corresponding contact element. It is contemplated that the sleeves may be constructed as separate elements, or may be an electrically insulative coating placed on the housing  36 . 
     Each sleeve  46  may have a slot formed therein for receiving a corresponding contact. For example, sleeve  46  may have a slot  48  formed therein. Contact  40  may be disposed within slot  48  such that lead  38  may electrically engage an upper portion of contact  40  while terminal  42  may electrically engage a lower portion (not shown) of contact  40 . Contact  40  may engage at least one elastomeric element as described in U.S. Pat. No. 5,069,629, issued to Johnson on Dec. 3, 1991. 
     Sleeve  46  may provide electrical isolation between contact  40  and housing  36 . Further, sleeve  46  may be replaceable. This may be particularly useful after a predetermined amount of wear occurs between the sleeve  46  and contact  40  due to friction and other damage mechanisms. 
     Since housing  36  may be made from a conductive material, housing  36  may provide EMI shielding to contact  40 . Further, it is contemplated that housing  36  may shield integrated circuit  32  from noise generated on, or by, traces on printed circuit board  34 . Finally, rib  44  of housing  36  may minimize crosstalk between contact  40  and an adjacent contact  50 . 
     It is contemplated that housing  36  may be grounded or otherwise electrically connected to a known voltage. In this configuration, the contact is surrounded by metal and an intervening dielectric, thereby yielding a strip-line structure. The geometries and certain other physical parameters thus define the impedance of the contact elements. 
     In another embodiment of the present invention, housing  36  may be formed from a plastic or other suitable dielectric or insulating material. Predetermined portions of housing  36  may then be coated or otherwise provided with a conductive surface. In a preferred embodiment, the inner surfaces of the ribs of housing  36  may be coated to minimize cross-talk between adjacent contacts. Further, it is contemplate that the top and side surfaces of housing  36  may be similarly coated to provide a shielding function. The conductive coating may be electrically coupled to ground. 
     An advantage of the embodiment shown in FIG. 2 is that the impedance of contact  40  is known and stabilized. In some prior art interconnect systems, the impedance of contact  40  may be dominated by stray capacitance and stray inductance, which may not terminate to a known voltage. The embodiment shown in FIG. 2 provides a ground plane and thus a majority of the impedance is terminated to ground. This may stabilize the bandpass of each contact up to the cutoff frequency thereof. 
     With reference to FIG.  1  and FIG. 2, housing  36  provides a first plate (or rib)  44  and a second plate (or housing)  36 , with contact  40  disposed therebetween. The impedance, as seen by contact  40 , is defined by the area of contact  40 , the distance between contact  40  and rib  44  and housing  36 , and the permittivity of sleeve  46 . By varying these parameters, the impedance of contact  40  may be designed to match, or correct for, the input impedance of the corresponding input of integrated circuit device  32 . In an illustrative embodiment, the distance between contact  40  and rib  44  is approximately 17 mils, but other distances are contemplated. 
     As indicated in U.S. Pat. No. 5,069,629, issued to Johnson, contact  40  is easily field replaceable. That is, each contact  40  may be removed and replaced with another contact. Thus, it is contemplated that a number of contacts, each having a different area, may be provided to a user along with a housing. The user may determine the input impedance of each input of a corresponding integrated circuit. The user may then provide an appropriate contact into each slot within housing  36  such that the impedance of each contact may match, or correct for, the input impedance of the corresponding inputs of the integrated circuit device. Thus, the user may: (1) determine the desired impedance of a contact element; (2) select a contact element that will result in the desired impedance; and (3) provide the contact selected in step (2) into a corresponding slot within a housing. In this way, a user may program the impedance of each contact within the interconnect device for each integrated circuit input to be tested. 
     FIG. 3 is a perspective view showing a housing in accordance with the first embodiment of the present invention. The drawing is generally shown at  60 . A housing  61  comprising an electrically conductive material is provided. In a preferred embodiment, housing  61  is manufactured from aluminum, but it is recognized that any conductive material may achieve similar results. Housing  61  may have a top surface  66  and a bottom surface  68  as shown. A number of slots, for example slots  80 , 82 , may be formed though housing  61 . Each of the slots  80 , 82  may extend from the top surface  66  through housing  61  to the bottom surface  68 . As a result of forming the number of slots  80 , 82 , a number of ribs may remain. For example, rib  84  may extend between slots  80  and  82 . Each rib  84  may be electro-mechanically coupled to housing  61 , thereby providing an electrical shield around the perimeter of slots  80  and  82 . 
     A sleeve may be provided within each of the slots. For example, sleeve  86  may be provided in slot  82 . It is contemplated that sleeve  86  may be manufactured from an insulating or dielectric material such as polytetrafluoroethylene. Each sleeve may have a slot formed therein for receiving a corresponding contact element. For example, sleeve  86  may have slot  88  formed therein for receiving a corresponding contact element. 
     A contact may then be provided in each slot of predetermined sleeves. For example, contact  74  may be provided within slot  88  of sleeve  86 . In this configuration, sleeve  86  may electrically isolate contact  74  from housing  61 . As indicated above, housing  61  may be electrically coupled to ground or to some other know voltage. Since housing  61  is made from a conductive material, housing  61  may provide EMI shielding to each of the contacts as shown. Further, the ribs of housing  61  may minimize crosstalk between adjacent contacts. Although not specifically shown, it is contemplated that any size, shape or type of contact element may be used in conjunction with the present invention. This includes both rigid planer contact elements, deformable contact elements, or any other type of contact elements. 
     Referring specifically to housing  61 , a first trough  62  may be provided in the top surface  66  thereof extending in a downward direction therefrom. A second trough  64  may be provided in the bottom surface  68  thereof extending in an upward direction therefrom, wherein the first trough  62  is laterally offset from the second trough  64 . A first support element (not shown) may be disposed in the first trough  62  and a second support element (not shown) may be disposed in the second trough  64 . The first and second support elements may be made from a rigid or elastomeric material. Each of the number of contacts may engage the first and second support members. A further discussion of the contact support structure may be found in U.S. Pat. No. 5,069,629, issued to Johnson on Dec. 3, 1991. 
     In a preferred embodiment, one or both of the first and second support elements (not shown) are made from an elastomeric material. This allows each of the contact elements to move both laterally and vertically when engaged by a device lead. The movement of the contacts may provide a wiping action to both the leads of an integrated circuit and the terminals of a printed circuit board. The embodiment shown in FIG. 3 allows the desired contact motion while maintaining a relatively constant impedance. 
     The embodiment shown in FIG. 3 has the advantage that the impedance of each contact may be known and stabilized as described with reference to FIG.  2 . Thus, it is contemplated that a number of contacts, each having a different area, may be provided to a user. The user may determine the input impedance of each input of a corresponding integrated circuit. The user may then select and provide an appropriate contact into each slot within housing  61  such that the impedance of each contact may match, or correct for, the input impedance of the corresponding inputs of the integrated circuit device. Thus, the user may: (1) determine the desired impedance of a contact element; (2) select a contact element that will result in the desired impedance; and (3) provide the contact selected in step (2) into a corresponding slot within a housing. In this way, a user may program the impedance of each contact within the interconnect device for each integrated circuit input to be tested. 
     FIG. 4 is a perspective view with some parts cut away showing a second embodiment of the present invention in combination with a printed circuit board. The diagram is generally shown at  100 . A housing  102  is provided. It is contemplated that housing  102  may be formed from an electrically conductive material. Although aluminum is the preferred material, it is recognized that any electrically conductive material may achieve similar results. Housing  102  may have a number of slots  104 , 106  formed therein. Each slot  104  and  106  may be separated by a rib  108 . Rib  108  may be electro-mechanically coupled to housing  102 . Each slot may have at least one spacing member  110  disposed therein. In the embodiment shown in FIG. 4, slot  104  has four spacing members  110 ,  112 ,  114 , and  116  disposed therein. Each of the four spacing members  110 ,  112 ,  114 , and  116  may be positioned in one of the four corners of slot  104 . Thus, spacing member  110  is laterally spaced from spacing member  112 . Similarly, spacing member  114  is laterally spaced from spacing member  116 . In a preferred embodiment, spacing members  110 ,  112 ,  114 , and  116  may be formed from polytetrafluoroethylene. It is recognized, however, that a user may select an insulating material which has a desired permittivity thereby providing the desired impedance characteristics to a corresponding contact element. 
     A contact  120  may be provided within slot  104  such that an upper portion of contact  120  is positioned between spacing members  110  and  112 , and a lower portion of contact  120  is positioned between spacing members  114  and  116 . In this configuration, contact  120  is prevented from electrically contacted a sidewall of slot  104 . Furthermore, the dielectric material extending between contact  120  and rib  108  and housing  102  is substantially comprised of air, except for the portions of contact  120  which engage spacing members  110 ,  112 ,  114 , and  116 . It is known that air has a low permittivity value and therefore may minimize the capacitance between contact  120  and rib  108  and housing  102 . This may increase the bandpass and/or cut-off frequency of contact  120 . 
     FIG. 5 is a perspective view with some parts cut away showing a third embodiment of the present invention in combination with a printed circuit board. The drawing is shown generally at  140 . This embodiment is similar to the embodiment shown in FIG. 4 except the spacing members  110 ,  112 ,  114 , and  116  are removed. Rather, each contact  142  and  144  may have an insulating layer provided directly on the lateral outer surfaces thereof. For example, contact  142  may have a first insulating layer  146  provided on a first surface thereof and a second insulating layer  148  on a second surface thereof. It is contemplate that the first and second insulating layers  146  and  148  may be provided on contact  142  via an adhesive, a deposition process, a subtractive process, or any other means. The first insulating layer  146  and the second insulating layer  148  may prevent contact  146  from electrically contacting housing  150 . The same attendant advantages discussed above may be provided by this embodiment as well. 
     FIG. 6 is a perspective view showing a housing in accordance with a fourth embodiment of the present invention. The diagram is generally shown at  170 . This embodiment is related to the first embodiment shown and describe with reference to FIG.  3 . However, in this embodiment, it is contemplated that preselected ribs of the housing may extend upward beyond the top surface of the housing and toward a corresponding integrated circuit device as shown. For example, ribs  178 ,  180 , and  182  may extend above top surface  174  of housing  172 . As indicated above with reference to FIG. 2, a lead of an integrated circuit may electro-mechanically engage each of the contacts. For example, a lead of an integrated circuit may electro-mechanically engage contact  184 . Thus, the lead of the integrated circuit may pass in between ribs  180  and  182 . Ribs  180  and  182  may thus provide electromagnetic shielding to the top portion of contact  184  and to at least a portion of the corresponding lead (not shown). Further, the impedance matching effects discussed above may be applied to both the contact  184  and the corresponding lead (not shown). 
     Another feature of the embodiment shown in FIG. 6 is an EMI skirt provided along the bottom perimeter of housing  172 . It is contemplated that a skirt  190  may be provided between housing  172  and a corresponding printed circuit board. Skirt  190  may be formed from any conductive material. However, in a preferred embodiment, skirt  190  may be formed from a wire mesh which may be compressed as housing  172  is brought into engagement with a corresponding printed circuit board (not shown). Skirt  190  may provide EMI shielding to the lower portion of the contacts and/or the terminals on the printed circuit board. 
     Another feature of the embodiment shown in FIG. 6 is a conductive gasket  192 . It is contemplated that conductive gasket  192  may be provided between housing  172  and a corresponding printed circuit board. Conductive gasket  192  may be formed from any conductive material. In a preferred embodiment, however, conductive gasket  192  may be formed from a metallic material or a wire mesh. Conductive gasket  192  may provide EMI shielding to the lower portion of the contacts and/or the terminals on the printed circuit board. It is contemplate that skirt  190  and conductive gasket  192  may be used together or individually, depending on the particular application. 
     FIG. 7 is a side elevational view showing a housing in accordance with the first embodiment of the present invention with a wire mesh placed over the top surface thereof. The diagram is generally shown at  200 . A housing  202  may be provided, wherein the housing may be made from a conductive material such as aluminum. It is recognized, however, that any conductive material may be used for housing  202 . 
     As described with reference to FIG. 3, a number of contacts, for example contact  204 , may be received within a number of slots. A sleeve may be provided in each of the number of slots within the housing  202 . The construction of the contact, sleeve, and housing is further described with reference to FIG.  3 . 
     An integrated circuit device  206  having a number of leads, may be brought into electro-mechanical engagement with the number of contacts of the interconnect device. For example, lead  208  of integrated circuit device  206  may be brought into electromechanical engagement with contact  204  of the interconnect device. The lower portion of selected contacts may be in electromechanical engagement with selected terminals on a printed circuit board. Thus, the interconnect device  200  may electro-mechanically couple a lead of integrated circuit device  206  with a corresponding terminal on a printed circuit board. 
     It is contemplated that an offset  207  may be positioned between housing  202  and integrated circuit device  206 . In a preferred embodiment, offset  207  may be part of housing  202  and may be made from a conductive material. Since housing  202  may be grounded, offset  207  may provide a direct ground connection to integrated circuit device  206 . This may be particularly useful when integrated circuit device  206  is packaged such that a ground plane thereof is positioned adjacent offset  207 . Further, offset  207  may provide a thermal sink to integrated circuit device  206 . Finally, offset  207  may provide a body stop to prevent damage to the leads  208  of integrated circuit  206  and to contacts  204 . 
     In the embodiment shown in FIG. 7, a conductive mesh  210  may be provided over the top of integrated circuit device  206 . The conductive mesh may be electrically connected to the outer periphery or other predefined portion of housing  202 . It is contemplated that conductive mesh  210  may be a wire mesh. It is further contemplated that conductive mesh  210  may comprise a conductive cover or similar structure which is electrically coupled to housing  202 . A purpose of conductive mesh  210  is to provide EMI shielding to the upper portion of the contacts, the leads of the integrated circuit device  206 , and the integrated circuit device  206  itself. 
     The density of the wire mesh may vary depending on the particular application. For example, the density of the wire mesh may be lower if only relatively low frequency EMI is to be shielded. Conversely, the density of the wire mesh may be higher if relatively high frequency EMI is be shielded. Thus, the wire mesh may be designed to accommodate a wide variety of applications. 
     FIG. 8A is a side perspective view of an S-shaped contact as used in the present invention. The diagram is generally shown at  220 . In a preferred embodiment, a contact  222  is S-shaped and dimensioned such that a first hook portion  224  engages a first support member (not shown) and a second hook portion  226  engages a second support member (not shown). In a preferred embodiment, contact  222  is formed from a beryllium-copper alloy. A further discussion of the contact support structure may be found in U.S. Pat. No. 5,069,629, issued to Johnson on Dec. 3, 1991. 
     With reference to FIG. 1, the capacitance of a contact element is generally given by the formula C=ε·A/D. The area of contact  222  is defined by a contact length  230  and a contact width  228 . In a preferred embodiment, the contact  222  is dimensioned to maintain the position of the first and second hook portions  224 ,  226 . This may be necessary to allow the first and second hook portions  224 ,  226  to physically engage the first and second support members (not shown). In one embodiment, this may be accomplished by substantially maintaining the contact length  230 . Thus, it is contemplated that the impedance of the contact element  222  may be varied by reducing the contact width  228  or varying other design parameters of contact  222 . 
     It is contemplated that a number of contacts, each having a different area as described above, may be provided to a user. The user may determine the input impedance of each input of a corresponding integrated circuit. The user may then provide an appropriate contact into each slot within a housing such that the impedance of each contact may match, or correct for, the input impedance of the corresponding inputs of the integrated circuit device. Thus, the user may: (1) determine the desired impedance of a contact element; (2) select a contact element having the desired impedance; and (3) provide the contact selected in step (2) into a corresponding slot within a housing. In this way, a user may program the impedance of each contact within the interconnect device for each integrated circuit input to be tested. 
     It is further recognized that the distance from the contact to a corresponding rib may be varied to change the impedance of a corresponding contact. This may be accomplished by changing the thickness of the contact or providing a larger distance between adjacent ribs in the housing. Further, it is recognized that the permittivity of a corresponding sleeve may be varied by substituting various materials therefor to change the impedance of a corresponding contact. As indicated with reference to FIG. 4, it has already been disclosed that air may be used as an insulating material. Other materials are also contemplated. 
     FIG. 8B is a side perspective view of an S-shaped contact as used in the present invention with a predetermined portion removed therefrom. The diagram is generally shown at  240 . A contact element  242  having a removed portion  244  may be provided. The removed portion  244  may reduce the overall area of contact element  242 . As indicated with reference to FIG. 8A, it is preferred that the position of the first and second hook portions  246  and  248  remain relatively fixed because the first and second hook portions  246 ,  248  must physically engage the first and second support members (not shown). In the embodiment shown in FIG. 8B, the outer dimensions of contact element  242  are substantially the same as the outer dimensions of contact element  222  of FIG.  8 A. The impedance of contact element  242  may be varied by removing a predetermined portion of contact element  242  as shown. It is contemplated that any portion of contact element  242  may be removed as long as the position of the first and second hook portions  246 ,  248  remains relatively fixed. 
     FIG. 8C is a side perspective view of an S-shaped contact as used in the present invention with a number of predetermined portions  261  removed therefrom. The diagram is generally shown at  260  wherein a contact element  262  is shown. This embodiment is similar to the structure shown in FIG.  8 B. However, rather than removing a single portion from the contact element, it is contemplated that a number of portions may be removed from contact element  262  as shown. This may reduce the overall area of contact element  262 . 
     As indicated with reference to FIG. 8A, it is preferred that the position of the first and second hook portions  264  and  266  remain relatively fixed because the first and second hook portions  264 ,  266  must physically engage the first and second support members (not shown). In the embodiment shown in FIG. 8C, the outer dimensions of contact element  262  are substantially the same as the outer dimensions of contact elements  222  and  242 . The impedance of the contact element  262  may be varied by removing a number of predetermined portions from contact element  262  as shown. It is contemplated that any number of portions may be removed from contact element  262  as long as the position of the first and second hook portions  264 ,  266  remains relatively fixed. 
     FIG. 9A is a perspective view of a sleeve as used in the first embodiment of the present invention with a predetermined portion removed therefrom. The diagram is generally shown at  300 . In a preferred embodiment, sleeve  302  is positioned within a corresponding slot within a housing. Since it is contemplated that the slots in the housing may be uniformly dimensioned, it is desired that each sleeve  302  have the same outer dimensions. 
     With reference to FIG. 1, the capacitance of a contact element is given by the formula C=ε·A/D. The sleeve  302  may be made from an insulating material having a preselected permittivity. Thus, the impedance of a contact element may be varied by changing the permittivity of the dielectric or insulating material which is disposed between the contact element and the housing. In the embodiment shown in FIG. 9A, a portion  304  may be removed from sleeve  302 . Thus, the permittivity of the area between the contact element and the housing is defined by the insulating material for part of the contact area, and defined by air for the remaining contact area. By dimensioning the portion  304  that is removed from sleeve  302 , a desired impedance may be selected for each contact in the interconnect device. 
     It is contemplated that a number of sleeves, each having a different sized removed portion, may be provided to a user. The user may determine the input impedance of each pin of a corresponding integrated circuit. The user may then insert an appropriate sleeve into each slot of the housing such that the impedance of each contact may match, or correct for, the input impedance of the corresponding inputs of the integrated circuit device. Thus, the user may: (1) determine the desired impedance of a contact element; (2) select a sleeve that will result in the desired impedance; and (3) provide the sleeve selected in step (2) into a corresponding slot within a housing. In this way, a user may program the impedance of each contact within the interconnect device for each integrated circuit input to be tested. 
     FIG. 9B is a perspective view of a sleeve as used in the first embodiment of the present invention with a number of predetermined portions removed therefrom. The diagram is generally shown at  310  wherein a sleeve  312  is shown. This embodiment is similar to FIG.  9 A. However, rather than removing a single portion from the sleeve, a number of predetermined portions  311  may be removed, as shown. 
     FIG. 10 is a perspective view showing a housing in accordance with the first embodiment of the present invention, wherein a number of S-shaped contacts having varying impedance characteristics are preselected and inserted within corresponding slots within the housing. The diagram is generally shown at  330 . A housing  332  comprising an electrically conductive material is provided and is substantially similar to that shown and described with reference to FIG. 3. A number of slots, for example slots  334 , 336 , and  338 , may be formed though housing  332 . As a result of forming the number of slots  334 , 336 , and  338 , a number of ribs remain therebetween. For example, rib  340  may extend between slots  334  and  336 . Each rib  340  is electro-mechanically coupled to housing  332 , thereby providing an electrical shield around the perimeter of each of the slots. 
     A number of sleeves may be provided within each of the slots. For example, sleeve  344  may be provided in slot  338 . It is contemplated that sleeve  344  may be manufactured from an insulating or dielectric material. Each sleeve may have a slot formed therein for receiving a corresponding contact element. For example, sleeve  344  may have slot  346  formed therein for receiving a corresponding contact element  348 . 
     A preselected contact may then be provided within each of the slots of the number of sleeves. For example, contact  348  may be provided within slot  346  of sleeve  344 . In this configuration, sleeve  344  electrically isolates contact  346  from housing  332 . In a preferred embodiment, housing  332  is electrically coupled to ground or to some other known voltage. Since housing  332  is made from a conductive material, housing  332  may provide EMI shielding to each of the contacts therein. Further, the ribs of housing  332  may minimize crosstalk between adjacent contacts. 
     Referring specifically to the embodiment shown in FIG. 10, it is contemplated that a number of contacts  348 , 350 , 352 , each having a different area and thus a different impedance characteristic, may be provided to a user of the interconnect device. The user may determine the input impedance of each input of a corresponding integrated circuit. The user may then provide an appropriate contact, as shown, into each slot within housing  332  such that the impedance of each contact may match, or correct for, the input impedance of the corresponding inputs of the integrated circuit device. Thus, the user may: (1) determine the desired impedance of a contact element; (2) select a contact element that will result in the desired impedance; and (3) provide the contact selected in step (2) into a corresponding slot within the housing. In this way, a user may program the impedance of each contact within the interconnect device for each integrated circuit input to be tested. 
     It is further contemplate that the user may: (1) determine the desired impedance of a contact element; (2) select a sleeve that will result in the desired impedance; and (3) provide the sleeve selected in step (2) into a corresponding slot within a housing. In this way, a user may program the impedance of each contact within the interconnect device for each integrated circuit input to be tested. 
     Finally, it is contemplated that a user may: (1) determine the desired impedance of a contact element; (2) select a sleeve and contact combination that will result in the desired impedance; and (3) provide the sleeve and contact combination selected in step (2) into a corresponding slot within a housing. This may provide additional flexibility in achieving the desired contact impedance. 
     New characteristics and advantages of the invention covered by this document have been set forth in the foregoing description. It will be understood, however, that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of parts, without exceeding the scope of the invention. The scope of the invention is, of course, defined in the language in which the appended claims are expressed.