Abstract:
An apparatus and method for positioning an integrated circuit (IC) for test in a test assembly. An IC positioning mechanism is provided that permits ready resetting of the position of the device that mounts an IC onto a test socket, thereby permitting efficient modification of a test assembly to accept different sized ICs. A mechanism for preventing inadvertent opening of the test assembly is also disclosed.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Application No. 60/330,280, filed Oct. 17, 2001, entitled Apparatus and Method of Setting IC Mounting Mechanism in Test Equipment and having the same inventor(s) as above. 

   FIELD OF THE INVENTION 
   The present invention relates to integrated circuit (IC) test equipment and, more specifically, to securely, rapidly and safely positioning an IC under test in that test equipment. 
   BACKGROUND OF THE INVENTION 
   There has been a prolific growth in the production of ICs and an increase in the number and type of products that incorporate ICs. Some ICs, such as memory chips and some processors, are made in such large quantities that they are sometimes regarded as commodity items. 
   ICs typically consist of a semiconductor substrate or die that is mounted in a package. The package is often a plastic and/or ceramic casing that distributes the densely arranged contact pads of the die to an array of pins or other extensions that extend from the package and permits the IC to be mounted to a printed circuit board or other substrate. Note that while lead or pin packages are referred to predominantly herein, the present invention applies as well to ball grid array, beam lead, flip-chip mounting and other IC mounting techniques. 
   Typical development of an IC includes the steps of design, fabrication, prototype testing, redesign (modification based on test results), prototype re-testing and larger scale manufacture. It is critically important at all stages of the IC development and production chain, i.e., prototype development through quality assurance, to provide rapid and accurate testing of an IC. 
     FIG. 1  illustrates a representative prior art testing assembly for testing packaged ICs. The testing assembly  10  includes a base  12  having a test socket  14  and a lid  20  having an IC mounting mechanism  30 . In the perspective of  FIG. 1 , socket  14  is shown as extending above base  12  so that it may be seen, though it is typically recessed below the top surface of base  12 . 
   In use, an IC  18  is positioned over socket  14  such that pins  17  align with corresponding holes  15  in the socket. The hinged lid  20  is shut and the IC mounting mechanism is actuated to assert a distributed force onto the IC that pushes the pins of the IC a sufficient distance into holes  15 . The IC mounting mechanism includes a screw-based positioning mechanism  31  that determines the distance by which the pins are seated into the holes and a pressure plate  22  that more evenly distributes the force of the positioning mechanism. 
   The positioning mechanism includes a cylindrical screw  32 , an annular disk  34  and coupling screws  35 . These components engage a threaded hole  24  in lid  20  and a stop pin  26  mounted on the top of lid  20 . The cylindrical screw  32  threads into hole  24  and the annular disk has a ¾ rotation length recessed groove  36  on its underside that fits over pin  26 . The relative position of the annular disk and the cylindrical screw are set by screws  35  with the cylindrical screw threaded into hole  24  and the annular disk mounted such that groove  36  is positioned about pin  26 . The relative position of the cylindrical screw and the annular disk is maintained by the coupling screws  35 . To seat an IC into socket  14 , the annular disk is turned ¾ rotation (the length of groove  36 ) which pushes the pressure plate down an appropriate distance to securely seat the IC on the socket in a manner that does not damage pins  17  or other aspects of the chip, package or test equipment. 
   To establish the appropriate depth of cylindrical screw  32  below lid  20 , it is necessary to connect these two components at a first relative position, mount an IC in test assembly  10  and run an IC test program to confirm whether all of the pins  15  are properly contacted. If the pins are not properly contacted, then coupling screws  35  are unscrewed, the relative position of the annular disk and cylindrical screw is repositioned, screws  35  are re-tightened, the lid is closed, the annular disk is turn ¾ rotation to mount the IC onto the socket, and the IC pin seating test program is run again. This multiple step setting procedure is repeated until the annular ring and cylindrical screws are positioned to appropriately seat an IC each time. 
   This positioning, screwing, testing, repositioning, etc., procedure is undesirably time consuming and adds significantly to the cost of prototype assessment and IC production. The disadvantageous aspects of this multiple-step test setup procedure are compounded by the fact that different ICs have different sized packages and the multiple-step test setup procedure must necessarily be repeated for each type of IC under test. 
   A need thus exists for more efficiently and economically accommodating different sized ICs and IC packages in IC test equipment. 
   Another relevant aspect of the present invention is providing a security mechanism that prevents a test operator from inadvertently opening a test assembly, i.e., opening the assembly before releasing the pressure asserted by the IC mounting mechanism. Opening the lid before rotating the mounting mechanism back ¾ rotation (or the like) can cause the lid to fly open with significant force, potentially causing damage to the operator or equipment. Furthermore and perhaps more importantly, if the positioning mechanism is not repositioned upward before mounting, then as the lid is pivoted closed, the portion of the pressure plate closest to the hinge will contact the IC first and force the IC onto the socket at an angle, as opposed to a uniform force from above. Mounting an IC at an angle is far more likely to cause pin damage and mis-alignment. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an object of the present invention to provide an IC test assembly that permits ready adjustment of the IC positioning mechanism. 
   It is another object of the present invention to provide an IC test assembly that does not utilize fixed fastener-based adjustment of the IC positioning mechanism, as discussed above in the prior art embodiments. 
   It is another object of the present invention to provide an IC test assembly that permits bias-release based adjustment of the IC positioning mechanism. 
   It is also an object of the present invention to provide a security mechanism for an IC test assembly that prevents both inadvertent opening of the assembly and opening prior to withdraw of the IC mounting force. 
   These and related objects of the present invention are achieved by use of an apparatus and method for positioning an integrated circuit for test as described herein. 
   The attainment of the foregoing and related advantages and features of the invention should be more readily apparent to those skilled in the art, after review of the following more detailed description of the invention taken together with the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a representative prior art testing assembly for testing packaged ICs. 
       FIG. 2  is a partial cross-sectional view of an IC test assembly incorporating an IC positioning mechanism in accordance with the present invention. 
       FIGS. 3-5  illustrate components of the IC positioning mechanism of  FIG. 2  in accordance with the present invention. 
       FIG. 6  is an exploded view of another embodiment of an IC positioning mechanism in accordance with the present invention. 
       FIGS. 7A-7E  illustrate components of the IC positioning mechanism of  FIG. 6  in accordance with the present invention. 
       FIGS. 8 and 9  illustrate the embodiment of  FIG. 6  in the engaged and unengaged positions. 
       FIGS. 10-12  illustrate a security mechanism for preventing inadvertent opening of an IC test assembly in accordance with the present invention. 
   

   DETAILED DESCRIPTION 
   Referring to  FIG. 2 , a partial cross-sectional view of an IC test assembly  110  having an IC mounting mechanism  130  that incorporates a screw-based IC positioning mechanism  131  in accordance with the present invention is shown. The arrangement of  FIG. 2  illustrates some of the same components illustrated in FIG.  1 . These include the base  112 , socket  114 , pins  117 , IC  118 , pressure plate  122 , lid  120 , threaded hole  124  and stop pin  126 . 
   IC positioning mechanism  131  includes a positioning screw  132 , an annular ring  133 , a positioning handle member  135 , fastening mechanism  137  and a biasing device  139 . In this particular embodiment, the fastening members are screws and the biasing devices  139  are coil springs. It should be recognized that other suitable fastening and biasing techniques may be employed without departing from the present invention.  FIGS. 3-5  illustrate the positioning screw, annular ring and handle member, respectively, in more detail. 
     FIG. 3  is a cross-sectional view of positioning screw  132 .  FIG. 3  illustrates that positioning screw  132  includes an annular ring region  145 , a threaded region  147 , a flange  162  and receiving holes  163  for receiving screws  137 . 
     FIGS. 4A-4C  are a top, cross-sectional and bottom view, respectively, of annular ring  133 .  FIGS. 4A-4C  illustrate that annular ring  133  has a ring body  171  which has one or more protrusions  172  rising from a top surface thereof and a stop pin receiving groove  173  having a preferred length of approximately ¾ of the ring&#39;s circumference formed in the bottom surface of the ring. 
     FIG. 5  illustrates a bottom view (from the perspective of  FIG. 2 ) of handle member  135 . Illustrated in  FIGS. 2 and 5 , handle member  135  includes walls  181  that extend from a relatively planar top portion  182 . Top portion  182  is preferably machined to have holes  183  that accommodate screws  137 . These holes are preferably countersunk on the top surface to accommodate spring  139  as shown in FIG.  2 . The top portion also includes a central bore opening  184  and a plurality of radially disposed recesses  185  into which the protrusion(s)  172  of the annular ring are inserted. The device of  FIG. 2  is said to be engaged when protrusions  172  are seated in recesses  185  and unengaged or disengaged when handle member  135  is lifted to remove protrusions  172  from the recesses. The disengaged position is shown in FIG.  2 . (Note that  FIG. 8  shows an engaged position). The recesses  185  are provided in a circumferentially shelf  186 . 
   Test assembly  110  and IC positioning mechanism  131  are preferably arranged and function as follows. Positioning screw  132  is preferably a hollow cylinder (to permit air passage through its interior shaft) and flange  162  extends past the screw threads so as to engage the top surface of the annular ring  133 . The annular ring is positioned such that groove  173  is mounted over stop pin  126 , and flange  162  maintains annular ring  133  and groove  173  over stop pin  162 . 
   Handle member  135  is fastened by screws  137  to the top of positioning screw  132 . As a result, movement of handle member  135  necessarily moves positioning screw  132 . Springs  139  bias the handle member onto the annular ring such that protrustions  172  are positioned into and maintained by recesses  185 . Note that  FIG. 2  illustrates the position of the handle member when lifted off of the annular ring, i.e., lifted upward in the direction of arrow A, compressing the springs and lifting the handle member out of engagement with protrusions  172  (the unengaged position). 
   Turning the handle member when protrusions  172  are lodged in recesses  185  causes the annular ring to move within the ¾ rotation distance allotted by groove  173 . Since the handle member is securely coupled to the positioning screw, movement of the handle member through this ¾ rotation results in a corresponding movement of the positioning screw. Accordingly, rotation of the handle member in the downward direction causes the positioning screw to move downward relative to lid  20  and push IC  118  onto socket  114  via pressure plate  122 . 
   If the positioning screw is not far enough down relative to lid  120  to adequately mount an IC (or if it is too far down), handle member  135  is lifted in the direction of arrow A such that protrusions  172  are no longer engaged in recesses  185 . The handle member can then be turned in a manner that does not turn the annular ring, but does turn the positioning screw a corresponding amount and inherently repositions the positioning screw. When the desired amount of repositioning is achieved, handle member  135  is released and reseated onto the annular ring such that protrusions  172  are inserted into recesses  185 . The handle member can then be turned in a manner that turns the annular ring and the positioning screw through the guarded ¾ rotation mounting movement. 
   To make fine adjustments, the handle member is simply lifted, turned slightly and set back down. This arrangement eliminates the repetitive and tedious multi-step test setup procedure of the prior art. 
   Suitable materials for the components discussed herein include plastics, metals and other suitable materials as generally known in the art. 
   Referring to  FIG. 6 , an exploded view of an alternative embodiment of a mechanism for positioning an IC for test in accordance with the present invention is shown.  FIGS. 7A-7E  illustrate further details of the components shown in FIG.  6 . IC Positioning mechanism  231  includes a positioning screw  232 , a bias spring  239 , a handle member  235 , an annular ring  233  and a fastening or “snap” ring  237 . 
   Screw  231  includes a complementary flange  240  (complementary to the shape of top depression  250  in handle member  235 , see below), a spring region  243 , an annular ring region  245 , snap ring groove  246  and thread region  247 . Handle member  235  includes a top depression  250 , a bottom depression  280 , a central opening  255  and recesses  285  that engage the protrusion  272  of annular ring  233 . The annular ring also includes a groove or groove like structure  273  for receiving stop pin  126  (of FIG.  2 ). 
   In use, positioning screw  232  is inserted through spring  239  and central opening  255  such that the spring and complementary flange are seated in top depression  250  of handle member  235 ; spring  239  generally located at spring region  243  and spring region  243  being of sufficiently narrow diameter to fit through central opening  255 . Annular ring  233  is then slipped over threaded region  247  of the positioning screw into place at annular ring region  245  and seated within the bottom depression  280  of the handle member. Fastening ring  237  is then snapped into groove  246  to maintain each of the above-described items in their respective positions. Positioning screw  232  is then screwed into threaded hole  124  in lid  120  until stop pin  126  is received in groove  273  and stops further rotation. IC positioning mechanism  231  operates in the same manner described for IC positioning mechanism  131  of  FIGS. 2-5 . 
   The positioning mechanism  231  of  FIGS. 6-7  is both similar and different from the positioning mechanism  131  of  FIGS. 2-5 . Similarities include, but are not limited to, the following. Complementary flange  240  shares the geometry of top depression  250 . Particularly, tabs  241  of flange  240  protrude into recesses  251  of the top depression (and fastening ring  237  holds screw  232  such that flange  240  cannot move above depression  250 ) so that movement of the handle member necessarily results in movement of the positioning screw. Thus, positioning screw  232  and handle member  235  are linked, similar to the arrangement of  FIG. 2  that utilized screws  137  to fasten the positioning screw and handle member. Furthermore, positioning mechanism  131  of FIG.  2  and positioning mechanism  231  of  FIG. 6  both operate by lifting the handle member against a bias force to disengage the handle member from the annular ring protrusions. An operator can then turn the handle member to set the positioning screw at a desired depth, then release the handle member such that recesses  285  re-engage the annular ring protrusions, thereby limited positioning screw movement to the ¾ rotation provided by the annular ring groove  273 . Another commonality is that flange  262 , between the spring region and the annular ring region, contacts the annular ring as does flange  162 . This is illustrated in more detail in  FIGS. 8 and 9 . 
   Differences, however, include that the locking relationship of the positioning screw and the handle member is not achieved with fasteners, but rather complementary, locking geometry and a snap ring that holds them in place. Among other beneficial aspects, this arrangement induces less friction during lifting or “disengagement” of the handle member, thus promoting increased ease-of-use and longer life. With respect to annular ring  270 , the groove of ring  131  has been replaced with an exterior ¾ circumferential recess that together with the interior of wall  281  functions as a “groove” that receives stop pin  126 . 
   Referring to  FIGS. 8-9 , partial cross-sectional views of IC positioning mechanism  231  in the engaged and unengaged positions in accordance with the present invention are respectively shown. Threaded region  247  is threaded a sufficient distance into hole  124  ( FIG. 2 ) that stop pin  126  seats itself in groove  273  (FIG.  8 ). Spring  239  is disposed about spring region  243  and biases handle member  235  onto annular ring  233 . The screw, handle member and annular ring are held in the position illustrated in  FIG. 8  by virtue of the bias force of spring  239  and the resistance of fastening ring  237 . 
   In  FIG. 8 , protrusions  272  are seated in recesses  285  formed in shelf  286 . Thus, rotation of handle member  235  moves annular ring  233  and screw  232  (via the geometry of tabs  241  and recesses  251 ). In the engaged position, the screw is limited to the amount of rotation (¾ in the present scenario) permitted by groove  273 . It should be recognized that while not specifically shown, the engaged position of IC mechanism  131  of  FIG. 2  operates in the same manner. 
   In  FIG. 9 , handle member  235  has been lifted in the direction of arrow A such that spring  239  is compressed and recesses  285  are lifted off of protrusions  272  (the annular ring staying down under the force of gravity). Handle member  235  can then be turned freely, moving screw  232  to a desired position relative to lid  120  and threaded hole  124 . The handle member can then be set back down such that the protrusions re-engage the recesses and the IC positioning mechanism is again constrained to the IC mounting movement, i.e., the guarded ¾ circumference rotation (or the like) defined by groove  273 . In a preferred embodiment, the threads for the positioning screw and the location of recesses on the underside of handle member  135 , 235  are configured to achieve a movement of positioning screw  132 , 232  relative to lid  120  of 0.005″ with each adjacent recess. 
   Referring to  FIGS. 10-12 , a security mechanism for preventing inadvertent opening of the test assembly in accordance with the present invention is shown. Latch  190  is provided with a J-hook  194  that hooks around roll pin  197 .  FIG. 10  is a perspective view with lid  120  partially raised. As the lid is lowered, stopping ledge  193  prevents latch  190  from swinging in too far such that the latch becomes positioned on the inside of roll bar  197 . Surface  195  is angle so that when the latch contacts the roll bar, the J-hook is pushed backward to swing via gravity back under the roll bar when the J-hook clears the bar in downward movement. Tab  191  extends from the front of the latch above pivot point hole. Depression of tab  192  causes the J-hook to swing out and clear of the roll bar for opening the assembly. Pivot rod  198  in lid  120  is preferably provided in a machined hole through lid  120  and pivot hole  192 . 
     FIG. 12  illustrates the test assembly in use. When handle member  235  is rotated to mount an IC into a test socket (via positioning screw  232  and pressure plate  122 ), the maximum gap between the lid  120  and base  112 , in one embodiment, is 0.040″. The depth of the hook, D H , in this exemplary embodiment is 0.035″. Thus, with pressure being exerted by the IC positioning mechanism, the latch cannot be moved enough to clear the roll pin. To open the device, the handle member has to be rotated in the direction opposite of mounting to release the tension on the lid. The lid may move into contact with the base, lessening the 0.040″ gap to zero such that the J-hook has 0.005″ clearance from which to be pivoted out and clear of roll pin  197  to “unlock” the lid. In this or like manner, inadvertent opening of the lid is prevented. In addition, the IC positioning mechanism is necessarily reset before the next IC mounting operation. 
   While the invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modification, and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth, and as fall within the scope of the invention and the limits of the appended claims.