Abstract:
A contact for testing an integrated circuit includes a contact body with multiple embedded links within the body having at least two axes of rotation. The contact body is hollow with cavities that house tubular resilient members to bias the embedded links in a first preferred orientation and position.

Description:
BACKGROUND 
     The present invention relates to sockets that electrically connect an integrated circuit with an IC board. More particularly, the present invention is directed to a thermal contact with an embedded flexible link that maximizes thermal and electrical contact for both signal and ground contacts while emphasizing scrub movement. Sockets, such as those used for testing or connecting an integrated circuit, utilize the thermal contacts to achieve a positive connection between an IC device under test (DUT) and a board, such as a load board of a piece of test equipment or other fixture. 
     Integrated circuit tester devices have long been used in the semiconductor industry to test and evaluate the quality of the chips off the manufacturing line. Signal integrity is a critical aspect of chip design and testing. To this end, it is desirable to maintain impedance through a conducting portion of a contact interconnecting the integrated circuit lead to its corresponding load board pad at a particular desired level. The effective impedance of the design is a function of a number of factors. These include width and length of conduction path, material of which the conductive structure is made, material thickness, etc. 
     When testing the electrical characteristics of a packaged or molded semiconductor device such as an integrated circuit (IC), it is common to utilize a specialized test socket that secures and connects the IC to the equipment that evaluates its performance, i.e. a load board. Many different test sockets have been devised for quickly and temporarily connecting integrated circuit leads of a chip to be tested to a load board of a tester. Automated test apparatus in particular use a number of such sockets. Typical socket arrangements use force brought to bear upon a contact positioned between a lead of the IC and the load board to deform a probe tip of the contact and engage a pad on the load board. Such a configuration provides for positive connection between the pins or contact pads of the DUT and corresponding leads of a test apparatus. Examples of this type of connection can be found, for example, in U.S. Pat. No. 6,409,521 to Rathburn, and U.S. Pat. No. 7,737,708 to Sherry, the teachings and contents of both of which are fully incorporated herein by reference. 
     Whether it is for testing integrated circuits or for mounting such circuits on a board, appropriate socket-like connectors are needed. Factors such as cost, having a low profile, and shortening the electrical signal path drive the industry to constantly seek to improve on the prior art sockets. A solution to the foregoing was provided by U.S. Pat. No. 7,918,669 to Tiengtum, and assigned to the present assignee, the contents of which are fully incorporated herein by reference. A feature of that device was a cylindrical elastomer that provided a resilient biasing of the connectors, which allowed the testing device to reliably make effective contact with the device under test (DUT). 
     It is important for such sockets to promote both thermal scrub and pad scrub when the DUT is placed in the socket. The present invention is designed to advance the contact and scrub characteristics of the contact with the DUT to increase the effectiveness and performance of the socket and contact. 
     SUMMARY OF THE INVENTION 
     The present invention is a contact having embedded resilient micro links enclosed on three sides with a protrusion that maintains contact in the Z direction. A cutout feature allows floating contact with a lollipop cutter, and a smooth flat base enhances contact with the tester. Micro links are spaced along the contact to coincide with electrical contacts on the DUT, and multiple pins can be implemented in a single contact. An elastomer member provides the resiliency for pin contact, and the pad scrub as well as the thermal transfer is advanced by the present invention. 
     These and many other features of the present invention will best be understood by reference to the following descriptions and figures. However, it is to be understood that while the inventor&#39;s best mode has been described and shown, the invention is not to be limited to any particular drawing or description. Rather, it is understood that there may be many variations of the present invention that would be readily appreciated by one of ordinary skill in the art, and the invention encompasses all such variations and modifications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  an elevated, perspective view of a socket used to test integrated circuits using the contact of the present invention; 
         FIG. 2  is an enlarged, partially cut away perspective view of the contact of the present invention; 
         FIG. 3  is an elevated, perspective view of the contact of the present invention outside of the socket; 
         FIG. 4  is a cross-sectional view along lines  4 - 4  of the contact of  FIG. 3 ; and 
         FIG. 5  is an exploded view of the contact of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  illustrates an integrated circuit test socket  40  of the type generally described in U.S. Pat. No. 7,918,669, the contents of which are incorporated herein. The test socket  40  has a generally square profile with up to four aligning holes  42  to mount the test socket on the testing equipment. On the test socket is a generally square recess  46  is formed to receive the integrated circuit chip under test. A plurality of electrical connectors are formed within the recess  46  as described more fully in the &#39;669 patent referenced above. Once the chip is placed in the recess  46 , the test socket  40  may be placed, for example, in a handler work press and clamped in the handler in anticipation of testing the integrated chip. Other arrangements, both automated and manual, are also possible with the present invention. 
       FIG. 2  illustrates a chip  14  (partially cut away) in the socket  40 , which the chip  14  makes electrical and thermal connection with a contact  20 . The connection between the chip  14  and the contact  20  is then evaluated by measuring a signal (thermal or electrical) that is measured at the contact  20  and relayed to the testing device. In this manner, the response of the chip to contact and temperature can be tested prior to shipment of the chip. 
       FIGS. 3-5  illustrate a first preferred contact  30  for the socket described above. The contact is a body of generally rectangular profile with a smooth bottom surface  32 , left and right sides  34 , a front surface  36 , a rear surface  38 , and an upper surface  48 . The contact body  30  has substantially smooth faces, with beveled edges  31  and the front and rear surfaces may include indentions  50  along a lowermost edge for aligning the contact with a tester. 
     The contact further includes a plurality of cavities  52  that are bored into the contact body  30 . Each cavity  52  has associated with it a first opening  54  in the upper surface  48  that allows a contact link to protrude through from its associated cavity  54 . Further, each cavity is also associated with a second opening  58  in either the adjacent side or the front surface, depending upon the location of the cavity. In most cases, the cavities closest to the ends of the contact body will have associated second openings in the sides  34  of the contact, while the remaining cavities have second openings  58  in the front surface  36  of the contact. The second openings allow the contact links to communicate with the tester by connecting the links to wires (not shown) that measure signal or temperature. 
     In each cavity  52  resides a resilient tubular member made of a polymer that can provide a biasing force on the contact links to maintain the links in an upright or inclined position. The resilient tubular members  62  are positioned in the respective cavities  52  through the selectively sized associated second openings  58  adjacent the first openings  54  on the upper surface  48 . In a preferred embodiment, the tubular members  62  are cylindrical but in each case have associated therewith a longitudinal axis. 
     Each cavity includes a designated contact link  64  positioned to make contact with an associated pin on the chip to be tested. Each contact link  64  is biased by a resilient tubular member  62  so as to extend from its associated cavity  52  through its associated first opening  54 . The contact links  64  are biased by its respective tubular member  62  in a first extended position toward the chip pin, and each contact link  64  is arranged for pivotal movement about an axis parallel to the axis of the respective tubular member. More specifically, in a preferred embodiment each cavity  52  includes a chamber  68  (see  FIG. 4 ) sized and shaped to receive a mating circular fulcrum  72  of a contact link  64  for pivoting movement therein. With the contact link&#39;s fulcrum  72  in the chamber  68  of the cavity  52 , the contact link rocks or pivots therein about an axis that is parallel to the longitudinal axis of the associated resilient tubular member  62 . 
     When a chip is placed on the contact  30 , the connectors of the chip bear against the contact links  64 , causing the links to pivot about their respective fulcrums  72  in a downward arc against the biasing of the resilient tubular member  62 . In this manner, solid and reliable contact is established with the chip at each connector, which can then be measured by transmitting a signal through the associated side/second opening. By controlling the placement of the tubular member  62  and the opening  54 , the direction of the rotation of each contact link  64  can be individually selected. That is, a rotation of a first contact link may be in a clockwise direction and a rotation of a second contact link is in a counter-clockwise direction when viewed from the left or right side surfaces. Moreover, rotation can also be about perpendicular axes, as shown in  FIG. 4 , where the rotation of a first contact link is in a longitudinal direction with respect to the contact body itself, and a second contact link rotates about a transverse axis of rotation orthogonal to the first axis of rotation. Thus, each contact link can be controlled to pivot or rotate is a specified direction as called for by the particular chip and application. 
     The contact body on the upper surface can include front and rear vertical spacers  82  to establish a limit for the chip to bear against the contact body  30 , where each vertical spacer  82  has a common height. The vertical spacers  82  are preferably adjacent at least two openings on the upper surface  48 , and more preferably at each end of the contact body. The upper surface of the contact body may further include a spacer platform  88  about a central first opening on the upper surface  48 , where the spacer platform  88  has a height that is equivalent to a height of the spacers  82 . 
     The front surface of the contact body  30  may include an elongate arcuate recess  94  extending horizontally therein for aligning the contact with a mating component on the testing device, or an adjacent second contact. 
     It will be understood that this disclosure is merely illustrative, and that it is to be further understood that changes may be made in the details, particularly in matters of shape, size, material, and arrangement of parts without exceeding the scope of the invention. Accordingly, the scope of the invention is as defined in the language of the appended claims, and is not limited in any manner by the aforementioned descriptions and drawings.