Abstract:
A test head for a semiconductor integrated circuit tester includes a main support structure defining a device interface board location, and a contact support frame that is displaceable relative to the main support structure for engaging a device interface board at the device interface board location. The contact support frame is composed of a first frame member having a first surface region that is directed towards the device interface board location and also having an opposite second surface region, a second frame member having a first surface region in spaced confronting relationship with the second surface region of the first frame member and also having an opposite second surface region, and a resilient mechanism effective between the first and second frame members for permitting the first frame member to move relative to the second frame member when force is applied to the second frame member at the second surface region thereof for displacing the contact support frame towards the device interface board location.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Subject matter disclosed in this application may be considered to be related to matter disclosed in U.S. patent application Ser. No. 10/802,993 filed Mar. 16, 2004 (CRED 2620); U.S. patent application Ser. No. 10/458,342 filed Jun. 9, 2003 (CRED 2666); U.S. patent application Ser. No. 11/024,528 filed Dec. 28, 2005 (CRED 3185); U.S. patent application Ser. No. 11/024,536 filed Dec. 28, 2004 (CRED 2664); U.S. patent application Ser. No. 11/096,337 filed Mar. 31, 2005 (CRED 2665), the entire disclosure of each of which is hereby incorporated by reference herein for all purposes. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This invention relates to a test head for a semicondcuctor integrated circuit (IC) tester.  
         [0003]     U.S. patent application Ser. No. 11/024,536 filed Dec. 28, 2004 describes a semiconductor integrated circuit tester comprising a test head that includes a circular device interface board (DIB) having an annular array of contact elements exposed at the underside of the DIB, and an annular support frame that is located below the DIB and is moveable vertically relative to the DIB. The support frame defines multiple radial slots that accommodate respective electrical connectors, which may be as described in co-pending patent application Ser. No. 10/802,993 filed Mar. 16, 2004. Each connector includes a cable positioning block in which the ends of multiple coaxial cables are held, with the conductive cores of the coaxial cables constituting contact elements that are exposed at the upper surface of the positioning block and vertically aligned with respective contact elements of the DIB. Ideally, the upper surfaces of the contact elements of the connector would all lie in a common horizontal plane and the lower surfaces of the contact elements of the DIB would all lie in a common horizontal plane so that vertical movement of the support frame would result in the contact elements of the connector simultaneously contacting the corresponding contact elements of the DIB. However, in practice the upper surfaces of the contact elements of the connector do not lie in a common horizontal plane and the lower surfaces of the contact elements of the DIB do not lie in a common horizontal plane.  
         [0004]     We can define the contact plane of a connector as the plane for which the sum of the squares of the distances of the upper surfaces of the contact elements of the connector from that plane is a minimum and similarly we can define the contact plane of the corresponding group of contact elements of the DIB as the plane for which the sum of the squares of the distances of the lower surfaces of the contact elements from that plane is a minimum. It is possible to manufacture the connector so that the variance in distance of the upper surfaces of the contact elements from the contact plane of the connector lies within a narrow range. Similarly, it is possible to manufacture the DIB so that the variance in distance of the lower surfaces of the contact elements in a given group from the contact plane lies within a narrow range.  
         [0005]     U.S. patent application Ser. No. 10/802,993 filed Mar. 16, 2004 discloses an interconnect system that is able to accommodate the variations in distance between the confronting contact elements due to manufacturing tolerances when the contact plane of the connector is parallel to the contact plane of the corresponding group of contact elements of the DIB, but the interconnect system may not be able to accommodate the variations in distance between the contact elements of the connector and contact elements of the DIB in the event that the contact planes are significantly out of parallel.  
         [0006]     One source of departures from parallelism of the contact plane of the connector and the contact plane of the corresponding contact elements of the DIB is nonuniformity in thickness of the DIB. Using conventional techniques it is possible to manufacture the DIB so that the upper and lower surfaces of the DIB are essentially planar, but it is more difficult to ensure that the upper and lower surfaces are parallel. For example, the DIB might vary in thickness by up to 2.5 mm along a diameter of the DIB. If the DIB is mounted so that its upper surface is horizontal, but the upper and lower surfaces of the DIB are not parallel, the lower surface of the DIB will not be horizontal.  
         [0007]     When the lower surface of the DIB is generally horizontal, the contact plane of a connector might nevertheless not be parallel to the contact plane of the corresponding group of contact elements of the DIB because of local departures from horizontal of the lower surface of the DIB or because the connector is mounted in the support frame in a manner such that its contact plane is not horizontal.  
       SUMMARY OF THE INVENTION  
       [0008]     In accordance with a first aspect of the present invention there is provided a test head for a semiconductor integrated circuit tester, the test head comprising a main support structure defining a device interface board location, and a contact support frame that is displaceable relative to the main support structure for engaging a device interface board at the device interface board location, the contact support frame comprising a first frame member having a first surface region that is directed towards the device interface board location and also having an opposite second surface region, a second frame member having a first surface region in spaced confronting relationship with the second surface region of the first frame member and also having an opposite second surface region, and a resilient mechanism effective between the first and second frame members for permitting the first frame member to move relative to the second frame member when force is applied to the second frame member at the second surface region thereof for displacing the contact support frame towards the device interface board location.  
         [0009]     In accordance with a second aspect of the present invention there is provided a test head for a semiconductor integrated circuit tester, the test head comprising a main support structure defining a device interface board location, a connector support frame that is displaceable relative to the main support structure for engaging a device interface board at the device interface board location, the connector support frame having a first surface region that is directed towards the device interface board location and a second surface region opposite the first surface region, and a connector member attached to the connector support frame in a manner permitting movement of the connector member relative to the connector support frame. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which  
         [0011]      FIG. 1  is a perspective view of a test head embodying the present invention,  
         [0012]      FIG. 2  is an enlarged partial sectional view of the test head, and  
         [0013]      FIG. 3  is a view taken on the line  3 - 3  in  FIG. 2 . 
     
    
       [0014]     For brevity, the following detailed description describes a test head embodying the invention when the test head is oriented in the so-called DUT up position. However, this is not intended to imply that the test head may not be used in other orientations, including the DUT down orientation, or that the claims should be limited to a particular orientation.  
       DETAILED DESCRIPTION  
       [0015]      FIG. 1  illustrates a test head  10  comprising a main support plate  14  to which a cylindrical outer housing  18  is attached. Alignment pins  20  are secured to the main support plate  14  and are used for docking the test head to failure analysis equipment such as an electron beam probe.  
         [0016]     The main support plate  14  defines a circular opening  16  ( FIG. 2 ). An annular cover plate  22  is attached to the outer housing  18 . A circular device interface board (DIB)  24  is accommodated within the cylindrical outer housing  18  and has a central region  24 A that is exposed through the central opening in the annular cover plate  22 . Several DUT sockets (not shown) are attached to the DIB in the central region  24 A for receiving respective semiconductor integrated circuit devices under test. Each DUT socket includes power supply pins for supplying operating power to the DUT and signal pins for supplying test signals to, and receiving test signals from, the DUT.  
         [0017]     The DIB  24  is formed with two concentric annular arrays of contact elements each comprising a via, the lower end of which is exposed at the underside of the DIB, and an annular contact pad surrounding the lower end of the via. The locations of the contact elements are illustrated schematically in  FIG. 1  by the dots on the cover plate  22 . The inner annular array of contact elements is composed of sixteen discrete groups  26  of contact elements (the locations of only two groups are shown) in respective sector-shaped regions of the inner array. The contact elements of the inner array include power supply contact elements that are connected through conductive traces of the DIB to the power supply pins of the DUT sockets. The contact elements of the inner array also include control signal contact elements. The outer annular array of contact elements is composed of sixty eight discrete groups  28  of contact elements (the locations of only two groups are shown) in respective sector-shaped regions of the outer array. The contact elements of the outer array are test signal contact elements and are connected through conductive traces of the DIB to the signal pins of the DUT sockets.  
         [0018]     Referring to  FIG. 2 , a cam ring  34  is located above the support plate  14  and within the outer housing  18 . The cam ring is coaxial with the outer housing and is formed with multiple helical cam slots  38 , only one of which is shown in the drawings. Cam followers  42  attached to the outer housing  18  project radially into the cam slots  38  respectively. The cam ring  84  is located in a manner that allows the cam ring to move vertically relative to the outer housing  18  and to rotate relative to the outer housing. The cam ring  34  is attached to a cam operating lever  46  ( FIG. 1 ) that can be actuated to rotate the cam ring relative to the outer housing and thereby raise or lower the cam ring relative to the main support plate  14 .  
         [0019]     Referring again to  FIG. 2 , an annular connector support frame  50  is located inside the outer housing  18  and is restrained against rotation within the outer housing  18 . The support frame  50  is located in a manner that allows it to move vertically relative to the main support plate  14  and is coupled to the cam ring  34  in a manner that permits rotational movement of the cam ring relative to the support frame but prevents vertical movement of the cam ring relative to the support frame. The support frame  50  defines multiple radial slots that accommodate respective electrical connectors  52 , which may be as described in copending patent application Ser. No. 10/802,993 filed Mar. 16, 2004.  
         [0020]     Each connector  52  includes a cable positioning block in which the ends of multiple coaxial cables  53  are held, with the conductive cores of the coaxial cables exposed at the upper surface of the positioning block. Above the cable positioning block is a contact device  54  comprising an insulating member having multiple C-shaped conductive elements accommodated therein.  
         [0021]     The DIB  24  is positioned over the support frame  50  and is captive beneath the cover plate  22 . Alignment elements (not shown) projecting from the outer housing  18  engage the DIB and thereby position the DIB relative to the outer housing. Alignment pins project upwards from the connectors  52  and are received in alignment bores of the DIB  24 , thereby positioning the connectors relative to the DIB, when the support frame is forced upward by actuation of the cam operating lever  46 .  
         [0022]     Each of the sixty eight groups  28  of contact elements on the lower surface of the DIB  24  corresponds to one of the connectors  52 , and the pattern of contact elements in each group  28  matches the pattern of the conductive cores of the coaxial cables  53  held by the corresponding connector.  
         [0023]     Still referring to  FIG. 2 , the support frame  50  comprises a lower frame  50 A and an upper frame  50 B. The lower frame  50 A is composed of inner and outer rings  60 ,  62  connected by radial webs  64 . The inner and outer rings of the lower frame each have multiple spring retaining bores  66  entering the ring at its upper axial end and extending parallel to the axis of the lower frame. The upper frame is similarly composed of inner and outer rings  70 ,  72  connected by radial webs  74  and the inner and outer rings  70 ,  72  each have multiple spring retaining bores  76  entering the ring at the lower axial end and extending parallel to the central axis of the upper frame. The spring retaining bores  66  of the lower frame are axially aligned with corresponding bores  76  of the upper frame and helical compression springs  80  are installed in the spring retaining bores so that one end of each spring  80  is received in a bore  66  of the lower frame and the opposite end of the spring is received in the corresponding bore  76  of the upper frame. In this way the springs  80  support the upper frame  50 B relative to the lower frame  50 A.  
         [0024]     Referring also to  FIG. 3 , the positioning block has an upper part  82  that is generally rectangular in external configuration, having two parallel longer faces that extend substantially radially of the annular frame and two parallel shorter faces perpendicular to the longer faces. Each of the two longer faces is formed with two grooves or channels  84  at opposite respective ends of the face. Thus, at each end of the upper part of the positioning block there is a pair of grooves  84 , the two grooves of a pair being at opposite respective sides of the positioning block.  
         [0025]     The positioning block is supported in its slot  64  in the support frame by two resilient retaining clips  88  made of spring steel or other material having similar mechanical properties. Each clip is substantially U-shaped when viewed in plan, having a base and two parallel limbs. The clips are applied to the positioning block by fitting the two limbs of each clip in one pair of grooves  84 . Referring to  FIG. 2 , the clips are attached to the upper frame  50 B by screws  90  that pass through the base of the U and are received in the inner and outer rings  70  and  72  respectively. The resilient nature of the clips allows limited movement of the positioning block relative to the support frame.  
         [0026]     When the cam operating lever  46  is actuated to raise the cam ring from its lower position to its upper position, the lower frame  50 A is correspondingly forced upward. As the lower frame rises, initially the upper frame  50 B moves with the lower frame. If the underside of the DIB is planar but is not perpendicular to the axis of movement of the lower frame  50 A, the connector  52  at one peripheral region of the support frame  50  will encounter resistance before the connectors  52  at other peripheral regions of the support frame, and the support frame is able to accommodate this departure from ideal conditions by permitting tilting of the upper frame relative to the lower frame as the lower frame continues to rise until the cam ring reaches its upper position. Accordingly, if the contact planes of the connectors are coplanar and the contact planes of the groups of contact elements of the DIB are parallel to the lower surface of the DIB and are coplanar, the tilting of the upper frame allows the contact planes of the connectors to be brought into substantially parallel relationship with the contact planes of the corresponding groups of contact elements of the DIB and allows sufficient force to be applied to all the connectors to establish electrically conductive pressure contact between the cores of the coaxial cables held by the connectors  52  and the corresponding contact elements on the lower surface of the DIB.  
         [0027]     In an embodiment of the invention, the structure of the support frame  50  is able to accommodate a variation in thickness of the DIB from about 3.75 mm to about 6.25 mm along a diameter of the DIB.  
         [0028]     In the event that the lower surface of the DIB is not planar, such that there are minor local variations in height of the underside of the DIB and the contact planes of the DIB are not coplanar, or the contact planes of the connectors are not coplanar, the spring clips  88  securing each positioning block to the upper frame  50 B allow tilting movement of the positioning block relative to the upper frame  50 B and allow a small amount of vertical movement of the positioning block relative to the upper frame  50 B, thereby accommodating these minor departures from parallelism and coplanarity.  
         [0029]     Provided that the contact plane of a connector is substantially parallel to the contact plane of the corresponding group of contact elements of the DIB, the C-shaped conductive elements of the contact device  54  provide electrical connections between the contact elements of the connector and respective contact elements of the DIB  24 .  
         [0030]     It will be appreciated that the invention is not restricted to the particular embodiment that has been described, and that variations may be made therein without departing from the scope of the invention as defined in the appended claims and equivalents thereof. Unless the context indicates otherwise, a reference in a claim to the number of instances of an element, be it a reference to one instance or more than one instance, requires at least the stated number of instances of the element but is not intended to exclude from the scope of the claim a structure or method having more instances of that element than stated. Further, a reference in the foregoing description to an element, be it a reference to one instance of that element or more than one instance, is not intended to imply that any claim should be interpreted as if it required that element or that embodiments of the invention could not be implemented without that element.