Test head manipulator

Abstract: A system is disclosed for positioning an electronic test head with respect to an electronic device handler. The positioner assembly includes separate locks which allow the test head to move vertically while preventing rotation of the test head about the main shaft. Thus, the test head can be aligned with the device handler, moved vertically away from the device handler while adjustments are made, and easily realigned with the device handler after adjustments have been completed. Alternatively, the separate locks allow the test head to rotate about the main shaft while preventing movement along the main shaft. Thus, the test head can be aligned with the device handler, rotated about the main shaft and away from the device handler while adjustments are made, and easily realigned with the device handler after adjustments have been completed. An index pin allows the test head to be rotated from an initial position to a temporary position and then rotated from the temporary position back to the initial position without requiring realignment of the test head relative to the device handler. The system includes a projected cradle assembly which allows the heavy test head to be projected above or below a physically large handler while still pivoting the load of the test head with its cable assembly at its center of gravity.

Description: FIELD OF THE INVENTION This invention relates to the field of art of electronic test head positioners. BACKGROUND ART In the automatic testing of integrated circuits (IC) and other electronic devices, special device handlers have been used which brings the device to the proper temperature and places the device to be tested in position. The electronic testing itself is provided by a large and expensive automatic testing system which includes a test head which has been required to connect to and dock with the device handler. In such testing systems, the test head has been usually very heavy - on the order of 40 to 300 kilograms. The reason for this heaviness is that the test head uses precision high frequency control and data signals so that the electronic circuits must be located as close as possible to the device under test. Accordingly, the test head has been densely packaged with electronic circuits in order to achieve the accurate high speed testing of the sophisticated devices. Test head positioner systems may be used to position the test head with respect to the device handler. When the test head is accurately in position with respect to the device handler, the test head and the device handler are said to be aligned. When the test head and device handler are aligned, the fragile test head and device handler electrical connectors can be brought together (i.e. docked), enabling the transfer of test signals between the test head and the device handler. Prior to docking, the fragile test head and device handler electrical connectors must be precisely aligned to avoid damaging the fragile electrical connectors. Test head positioners are designed in several configurations, each configuration being desirable for a particular purpose. In a tumble mode positioner, the test head pivots (or tumbles) about two oppositely disposed pivot points within a cradle. This enable the user to tumble the test head in the cradle from a position where the device handler interface board is up (for interface to horizontal plane handlers from the bottom), through 180 degrees, to a position where the device handler interface board is down (for interface to horizontal plane handlers from the top). In a cable pivot mode positioner, the test head pivots on the axis of the test head cables. Compared to the tumble mode positioner, a cable pivot mode positioner allows the use of reduced cable lengths. An example of a tumble mode positioner is disclosed in a previous patent by Smith (U.S. Patent No. 4,705,447). This patent discloses a positioner assembly which enables a test head to be moved for docking and undocking with respect to three vertical axes. In an alternative embodiment, the test head may be moved for docking and undocking with respect to two vertical axes and one horizontal axis. Thus, in either embodiment, the test head may be manipulated with six degrees of freedom with respect to the center of the plane defined by the test head electrical interface. Problems have been incurred in easily moving the heavy test head accurately into position with respect to the device handler mechanism. A common lock may prohibit both vertical motion and rotational motion of the test head about a main shaft. To move the test head vertically, the common lock is loosened, thus permitting rotational movement of the test head. Similarly, to rotate the test head, the common lock is loosened, thus allowing the test head to move vertically. However, when a test head is temporarily moved away from the device handler (i.e. undocked) so that adjustments or repairs can be made, both the vertical and the rotational position of the test head may need readjustment to ensure that the test head is aligned with the device handler. The large variety of orientations which the test head may assume may overwhelm an unskilled operator, thus making realignment difficult. Additional problems have been incurred in realigning the test head and the device handler after the test head has been moved away for repairs or adjustments. Some prior art manipulators include an additional point of rotation (i.e. an additional link) between the main shaft and the test head. By creating an additional link, the test head can be rotated about the axis defined by the link, thus maintaining the relative orientations of the remaining parts of the positioner. However, by adding additional links, the distance between the main shaft and the test head is increased, thus increasing the torque which is imposed by the test head on the main shaft bearings. Thus, the main shaft bearings, main shaft and main arm must become larger and more expensive to provide eased movement and reduced friction between manipulator parts under a greater load. Examples of cable pivot mode positioner are disclosed in a previous patent by Holt (U.S. Patent No. 4,893,074). Fig. 1 and Fig. 2 of this patent shows a first type of cable pivot mode positioner which is referred to as an opposite end cable pivot (OECP) style cradle assembly. As shown in Fig. 1 and Fig. 2, the test head is held at its center of gravity by the positioner. The cable and positioner are attached to the test head on opposite ends of the test head. Because the centerline of the device under test is desirably physically close to the centerline of the electrical outputs of the test head (located near the physical center of the test head) the OECP style cradle assembly may be inappropriate for use with large device handlers. This is because the OECP style cradle assembly cannot access, from underneath, horizontal plane handlers which are built like two pedestal office desks; the positioner stands where one pedestal of such a desk would be located. If the test head were to be projected away from the positioner assembly's support column so that the centerline of the device under test was physically close to the physical center of the test head, pivoting would not occur at the center of gravity of the horizontal wrist shaft, resulting in an unbalanced system. Similarly, in European patent publication 0 308 348, a test head that pivots (y) about one axis (12) through its center of gravity is disclosed. As shown in Figures 1 and 7 pivoting of the test head at an angle x occurs about shaft 91. Again, this results in an unbalanced system. Fig. 3 of the '074 patent shows a second type of cable pivot mode positioner which is referred to as a cable pivot with center of gravity offset (CPCG) style cradle. The CPCG style cradle allows somewhat more projection of the test head than the OECP style cradle. However, as with the OECP style cradle, the CPCG style cradle is unable to sufficiently project the test head without imposing overwhelming torque on the positioner assembly. Thus, to solve the interface problem, it is desirable to project the electrical output of the test head a large distance under or over the physically large handlers or probers so that the positioner itself can stand clear of the handlers or probers to which the test head is interfaced. It is also important to continue to enable the test head to pivot with six degrees of motion freedom about the center of gravity of the test head and cable assembly. For purposes of considering patentability, a brief patentability search was conducted. The patents identified to be of possible interest in the search were: U.S. Patent No. Inventor 3,262,593 William Hainer 4,345,847 Schiff et al. 4,229,136 Hugo Panissidi 4,132,318 Wang et al. 3,128,887 Guennec et al. SUMMARY OF THE INVENTION A system for positioning an electronic test head with respect to an electronic device handler. The system includes a projected cradle assembly which allows the heavy test head to be projected above or below a physically large handler while still pivoting the load of the test head with its cable assembly at its center of gravity. This provides the system with the freedom of six degrees of motion so that the heavy test head can easily interface to a physically large handler or prober in the horizontal plane. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagrammatic view of the system of Figs. 3-4 showing the docking of a test head in a projected cradle with the electrical interface of a handler; Fig. 2 diagrammatically shows the six degrees of freedom of the system of Fig. 1; Fig. 3 is a perspective view of the projected cradle assembly in accordance with the present invention; Fig. 4 is another embodiment of the present invention in which a plurality of shafts, oriented horizontally, and an offset cradle assembly is used; Figs. 5A-B show further embodiments of the invention with respect to securing the positioner system inside or alongside the test system; and Fig. 6 shows a further embodiment of the invention with respect to securing the positioner system in a test system cabinet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to Fig. 1, there is shown a test head positioner system 150 in accordance with the invention. As shown, positioner system 150 carries a test head 151 for a test system for docking with electrical contactor 167b of an integrated circuit handler 165. It will be understood that other electronic devices may be handled by the device handler, such as transistors, chips or dies, etc. In operation, positioner assembly 100 is moved manually in a substantially weightless condition to manipulate the heavy test head 151 accurately and precisely and dock it to handler 165. Docking is accomplished through the use of a docking assembly 170, attached to test head 151 and a docking gusset assembly 171, attached to the device handler 165. In docking, location pins 151a, 151b projecting from docking assembly 170 are inserted into corresponding openings 165a, 165b in docking gusset assembly 171 and electrical interface board 167a enters and mates with mating electrical contactor 167b which electrically connects the test head to the device to be tested. Electrical interface board 167a and electrical contactor 167b are collectively referred to as the electrical interface. As will later be described in detail, the position of test head 151 may be accurately manipulated in a substantially weightless condition to another position with six degrees of freedom to dock docking assembly 170 with other docking gusset assemblies in any position. For example, probers or handlers may be anywhere from a horizontal plane to a vertical plane. Furthermore, it is possible to undock the test head 151 from the electrical contactor 167b and to redock the test head 151 with electrical contactor 167b with a minimal amount of manipulation of the test head positioner assembly 100. Positioner system 150 includes a C-shaped beam forming a vertical housing or support column 45. Column 45 is supported at its bottom by a base assembly 103 having a base plate 108 and outwardly extending legs 109a through 109e which are bolted to the bottom of plate 108, for example. Wheel assemblies 115a through 115d are also bolted to the bottom of plate 108. Column 45 is secured to plate 108 by bolts (not shown) for example. Test head 151 is supported and manipulated in its docking by positioner assembly 100 which is adapted to move vertically on a main shaft 10. Assembly 100 comprises main arm tube 11, index lock plate 33, shoulder lock plate 32, upper arm assembly 27, forearm assembly 26, and projected cradle assembly 720. Positioner assembly 100 is adapted to ride vertically on main shaft 10 by a counter weight assembly (not shown) which moves vertically in either direction within the rear section of column 45. Additional weights (not shown) are added to exactly counterbalance the weight of assembly 100, together with the test head, so that the test head and assembly 100 are substantially weightless. Positioner assembly 100 includes main arm tube 11 which is disposed about main shaft 10. Main arm tube 11 moves vertically in either direction along main shaft 10. The upper end of main arm tube 11 is coupled to lock collar 12. Lock collar 12 is also located about main shaft 10 and is in turn coupled to the counter weight assembly situated within column 45. By tightening lock screw assembly 14, the vertical position of main arm tube 11 relative to main shaft 10 remains fixed. In an exemplary embodiment of the present invention, lock collar 12 may be implemented in accordance with that disclosed in U. S. Patent No. 4,715,574. It will now be understood that positioner assembly 100 simultaneously positions in 6 degrees of freedom, X, Y, Z,  x,  y,  z. As shown in Fig. 2, it is important for proper docking that test head 151 have 6 degrees of freedom so that electrical contactor 167b can accurately and effortless be positioned with respect to electrical interface board 167a, for example. The test head is moved with 6 degrees of freedom as described, for example, in U.S. Patent No. 4,527,942. The test head docks and undocks with the device handler using the docking apparatus, as described in U. S. Patent No. 4,705,447. Referring now to Figs. 1 and 3, there is shown an exemplary embodiment of the present invention. This embodiment includes forearm 26 which has a front "C" shaped section which rotatably receives wrist housing 705. Lock collar 139 is secured to the upper surface of forearm 26. Housing 705 rotates with respect to forearm 26 by way of vertical shafts 704a, 704b which extend through a vertical opening in lock collar 139, through a vertical opening in forearm 26, into wrist housing 705 and then from the bottom of wrist housing 705 into a lower opening in forearm 26. Shafts 704a, 704b are rigidly secured within wrist housing 705. Wrist housing 705 may be temporarily prevented from rotation by actuating lock screw assembly 114 which is formed within lock collar 139. Projected cradle assembly 720 includes outer cradle back 713 which is secured to wrist housing 705. Outer cradle back 713 is hollow with inner cradle back 714 located therein. Cradle pivot shaft 710 extends through one side of outer cradle back 713, through inner cradle back 714 and through the other side of outer cradle back 713, thus allowing inner cradle back 714 to pivot about cradle pivot shaft 710. Cradle side 707 is secured to inner cradle back 714 at substantially right angles through an opening in outer cradle back 713. The opening in outer cradle back 713 allows cradle side 707 to move up or down a minor distance as inner cradle back 714 pivots about cradle pivot shaft 710. By actuating lock screw assembly 711, which extends through an opening in outer cradle back 713 to inner cradle back 714, movement of cradle side 707 is prevented. Moving from wrist housing 705 to cradle pivot shaft 710, the distance between the top and bottom of outer cradle back 713 decreases. Moving from cradle pivot shaft 710 to cradle side 707, the distance between the top and bottom of inner cradle back 714 decreases. In a preferred embodiment of the present invention, inner cradle back 714 pivots about cradle pivot shaft 710 with + / - four degrees of motion. Cradle side 707 is attached to cable pivot housing 715, on its opposite end, thereby connecting inner cradle back 714 to cable pivot housing 715. Cable pivot housing 715 retains test head adapter ring 708 allowing ring 708 to rotate (in the  X direction) within cable pivot housing 715. The operation of cable pivot housing 715 and test head adapter ring 708 is more fully described in U.S. Patent No. 5,030,869. Test head yoke 709a, 709b is attached to test head adapter ring 708 and to the test head. In this exemplary embodiment  Z movement is provided by the rotation of the inner cradle back 714 about cradle pivot shaft 710. The  X movement is provided by the rotation of the test head 151 and yoke 709a, 709b via test head adapter ring 707 rotation within cable pivot housing 715. It will now be understood that positioner assembly 100 with this exemplary embodiment simultaneously positions and projects large test heads with 6 degrees of freedom over or under physically large handlers and probers. Thus, the test head may be accurately and effortlessly positioned with respect to the device to be tested as the test head and its cable assembly are rotated at their center of gravity. Referring now to Fig. 4, there is shown a further embodiment of the present invention in which forearm 26 is replaced with horizontal guide assembly 800. Horizontal guide assembly 800 includes linear guide block 810. Linear guide block 810 is fixedly attached to or integral with upper arm 27. Linear guide block 810 has linear bearings for receiving horizontal shafts 811 and 812. Bumper 813 is secured to one end of shafts 811, 812 to prevent shafts 811 and 812 from sliding out of the openings in horizontal guide block 810. The other end of horizontal shafts 811, 812 is secured to forearm 826. Horizontal shafts 811,812 may be temporarily prevented from linear motion by actuating lock screw assembly 804 which is formed within linear guide block 810. Forearm 826 is attached to horizontal guide assembly 800. Forearm 826 has a front "C" shaped section which rotatively receives wrist housing 829. Lock collar 839 is secured to the upper surface of forearm 26. Wrist housing 829 rotates with respect to forearm 826 by way of vertical shafts 840a and 840b (not shown). Vertical shaft 840a extends through a vertical opening in lock collar 839, through a vertical opening in forearm 826 and into wrist housing 829. Vertical shaft 840b extends through the bottom of wrist housing 829 into a lower opening in forearm 826. Shafts 840a and 840b are rigidly secured within wrist housing 829. Wrist housing 829 may be temporarily prevented from rotation by means of lock screw assembly 804 which is formed within lock collar 839. Wrist housing 829 includes a member 801 which projects from an end of wrist housing 829 at a substantially right angle. Horizontal wrist shaft 802 is attached to member 801 and is horizontally rotatable with respect to member 801. Horizontal wrist shaft 802 may be temporarily presented from rotation by actuating lock screw 814. Horizontal wrist shaft 802 is attached to projected cradle assembly 820. Projected cradle assembly 820 is fixedly attached to cradle side 890 which in turn is attached to cable pivot housing 883. Test head adapter ring 884 rotates within cable pivot housing 883 as described above with respect to the analogous components of Fig. 3. Yoke 853a, 853b is fixedly attached to test head adapter 884 and to the test head as described above with respect to Fig. 3. Referring to Fig. 5A, there is shown bottom plate 45e which is directly bolted on to the floor immediately next to test cabinet 1111c of the test system. For purposes of simplicity, the elements within column 45 have not been shown. In still another embodiment as shown in Fig. 5B, bottom plate 45e has connected to its lower surface, perpendicular legs 1170, 1171 connected to adjacent sidewalls of test cabinet 1111c. A leveling pad 1174 may be provided for the leveling of the base. Instead of being bolted to cabinet 1111c, bars 1170, 1171 may be extended (not shown) and coupled to two additional bars holding the remaining two sides of the cabinet. Thus, the four bars may be bolted to each other to rigidly engage cabinet 1111c. In still another embodiment of the present invention as shown in Fig. 6, the base 45e has been attached inside,the test system cabinet 1201. By controlling positioner assembly 100 by remote control, the test head can be projected by a long outer cradle back 713 to any desired distance. In this manner the complete column mechanism can be enclosed in the test system cabinet and all salient functions of the positioner system can be retained.

Claims: A system (150) including a support column (45) for positioning an electronic test head (151) for docking and undocking with an electronic device handler (165) and for providing rotation of said electronic test head (151) about the center of gravity of the test head and its cable assembly, said system (150) comprising: a projected cradle assembly (720) coupled to said support column (45), said projected cradle assembly (720) comprising: an outer cradle back (713) having a first end, a second end, and an opening; an inner cradle back (714) having a first end and a second end, said inner cradle back (714) extending through said opening and pivotably attached to said outer cradle back (713) at an axis located near the second end of said outer cradle back (713) and the second end of said inner cradle back (714); at least a part of said inner cradle back (714) located within said outer cradle back (713) so that said inner cradle back is free to pivot vertically upward and downward within and relative to said outer cradle back and about said axis; and means (708, 709) for coupling said test head (151) to said inner cradle back (714) for pivotable movement of said test head (151) about said center of gravity. The system of claim 1, wherein said outer cradle back (713) is tapered from said first end to said second end. The system of claim 1, wherein said inner cradle back (714) has a first end and a second end and said inner cradle back is tapered from said second end to said first end. The system (150) of claim 1, wherein said projected cradle assembly (720) further comprises means (711) for fixing the position of said inner cradle back (714) about said axis. The system (150) of claim 1, wherein an inner cradle side (707) is interposed between said inner cradle back (714) and said means (708, 709) for coupling said test head (151) to said inner cradle back (714). The system (150) of claim 1, wherein said axis is defined by a shaft (710). The system (150) of claim 5, wherein said inner cradle side (707) is coupled to said inner cradle back (714) near said first end of said inner cradle back (714). The system (150) of claim 5, wherein said inner cradle side (707) is coupled to said inner cradle back (714) at a substantially right angle. The system (150) of claim 1, wherein said support column (45) is housed within an enclosure (1201). The system (150) of claim 1, wherein said electronic test head (151) is moveable upwards and downwards by pivoting said inner cradle back (714) about said axis.

Inventors: HOLT ALYN R, HOLT, ALYN R.
Applicants: INTEST IP CORP, INTEST IP CORP.
Application year: 1992
Main classification: G01R1
IPC codes: B25J19, B25J9, G01R1, H01L21, B23Q1, G01R31