Patent Document

FIELD OF THE INVENTION 
   The present invention relates to a manipulator, particularly for positioning a test head on a device handler, comprising a holder for a test head and including a column on which the positioning means connected to the holder are arranged vertically positionable. 
   BACKGROUND OF THE INVENTION 
   One such manipulator serves to exactly position a test head relative to the device handler with which, for example, electronic devices, for instance ICs or wafers are furnished so that proper functioning of the devices can be tested by the test head. To obtain a true result, the relatively heavy test head needs to be advanced as near as possible to the device handler to ensure precise docking. This requires precise and smooth positioning of the manipulator positioning the test head three dimensionally. In addition, a compact design of the manipulator is called for since handlers for IC or wafer devices generally find application in a clean or ultraclean room environment requiring an economic footprint. 
   A manipulator of the aforementioned kind is described in German Patent DE 40 07 011 A1. This known manipulator comprises a vertical guide column on which a positioning means is arranged height-adjustable. The positioning means comprises an extension arm for pivoting in the horizontal plane and mounting a pair of dual articulated arms. At their end facing away from the extension arm the dual articulated arms are connected to a holder serving to secure a test head. 
   A generic manipulator is furthermore disclosed by the German Patent DE 35 24 348 A1.On this manipulator a pair of dual articulated arms is connected at one end to a test head and~at the other end to a height-adjusting lead screw. The dual articulated arms can be locked in position by clamping screws. 
   Although the dual articulated arm configuration on the known manipulators permits both linear displacement and pivoting of the test head in the horizontal plane, there is the disadvantage that the motion of the dual articulated arms cannot be repeated with the necessary accuracy when translational motion is combined with rotational motion. The fact that the manipulator known from German Patent DE 40 07 011 A1 comprises an extension arm permitting rotational motion in the horizontal plane also fails to change this situation. For, the rotational motion alone fails to make it possible to displace the test head sideways, for example. 
   SUMMARY OF THE INVENTION 
   The invention is based on the object of sophisticating a manipulator of the aforementioned kind such that motion of the test head in the horizontal plane is now achievable precisely and smoothly repeatable by a simple design with an economic footprint. 
   To achieve this object it is provided for on a manipulator having the aforementioned features as it reads from claim  1  that the positioning means comprise at least one pair of articulated arms spaced away from each other, each hinged at their one end to the holder and at their other end to a horizontally travelling carriage, the articulated arms being pivotable about a vertical axis and each carriage being movable independently of the other on the column. 
   A manipulator having such a configuration exploits having discovered that precise repeatability of the movement of the test head is attained when a pair of articulated arms pivotable in the horizontal plane is coupled to horizontally travelling carriages. This results in any movement of the test head being split into translational motion of the carriages and rotational motion of the articulated arms. Assigning each kind of motion to different positioning members, namely the articulated arms, on the one hand, and the carriages, on the other, assures replication in motion of the test head. Unlike prior art, this now makes it possible to arrange a locking means for docking the test head to a device handler on the holder. For, now, having to adjust the test head relative to the holder as needed in known manipulators, is eliminated due to precise replication in positioning the test head. 
   The horizontally travelling carriages additionally permit smooth positioning of the test head. Since each carriage can be moved independently of the other, the translational motion of the carriages and the pivoting motion of the articulated arms can now be combined into a rotational motion of the holder and thus of the test head in the horizontal plane in thus ensuring space-saving rotation of the test head. 
   Advantageous aspects of the manipulator in accordance with the invention form the subject matter of the sub-claims. 
   Thus, it is a favorable design aspect for the column to comprise linear guides extending vertically for linear translation of a slave actuator provided with guides for the carriages. The linear guides configured like known flat or dovetail guides permit precise positioning of the slave actuator and thus of the holder for the test head vertically. By the slave actuator mounting guides configured, for example, likewise as flat or dovetail guides, vertically positioning the carriages in synchronism is assured. 
   It is of advantage when the slave actuator and/or the carriages and/or the articulated arms can each be locked in position to permit positioning the holder and thus the test head in sequence three-dimensionally. Locking depends on the way in which the individual actuators are activated, for example, electrically or manually. Thus it is particularly expedient for manual actuation to provide arresting levers by means of which the slave actuator, the carriages and/or the articulated arms can each be positively locked in position. 
   It is furthermore of advantage when the holder comprises a mount for hinge-mounting the articulated arms. Such a configuration offers the advantage of. facilitating interchanging the holder in thus enabling a variety of test heads to be secured to the manipulator without involving complicated retrofitting. 
   Preferably the holder is pivotable about a horizontal transverse axis on the mount to result in an additional degree of freedom for moving the test head. This is particularly condusive in conjunction with a relatively heavy weight test head. In this case, the bending of the articulated arms caused by the heavy weight loading can be compensated by a corresponding inclination of the holder relative to the mount. Precisely setting the inclination between holder and mount is assured when in a further aspect of the present invention the holder is supported by an adjustable spacer on the mount. 
   The number of possibilities of freely moving the test head three-dimensionally is enhanced when to advantage the holder is arranged to rotate about its longitudinal centerline on the mount. Designing this is particularly simple by interposing a pivot bearing between holder and mount. To lead away the cable assembly as usually provided on a test head so that it is not damaged by kinking, experience has shown it to be particularly of advantage to provide the holder and mount with a through-passage which in addition contributes to a compact configuration in passing the cable assembly centrally through the holder. 
   In accordance with another particularly advantageous further embodiment of the manipulator in accordance with the invention the column comprises two upright posts spaced away from each other, each mounting at least one linear guide, the slave actuator clasping two opposing outer faces of the upright posts. Comprising the column as two upright posts makes it possible to route the cable assembly of the test head between the upright posts safe from being kinked. In addition, this enables a comparatively small spacing between holder and column to be achieved, resulting in not only a compact, but also a rugged configuration for handling the usually relatively very heavy test head. By providing each of the two upright posts with linear guides for the slave actuator, the flow of the forces is evenly divided by the two upright posts. Apart from this, providing for the slave actuator clasping two opposing outer faces of the upright posts ensures up and down travel in synchronism of the slave actuator along the two upright posts. 
   Preferably, the column is secured to a rotational plate to attain an additional vertical rotational motion. Such a rotational motion is required especially when the test head needs to be positioned between several device handlers or parked in a position for servicing. As an alternative or in addition thereto, the column may also be guided on rails to expedite travelling the manipulator between two positions. 
   In conclusion, in yet another advantageous further embodiment of the manipulator in accordance with the invention a counterweight assembly may be provided, comprising a counterweight connected to the slave actuator via a traction and pulley system, preferably comprising a cable, belt or chain. Such a counterweight assembly relieves the load on the articulated arms and carriages by the weight of the test head in thus contributing towards smooth, precise positioning of the test head three-dimensionally. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages of the present invention will now be detailed by the description of a preferred example embodiment with reference to the drawings showing the example embodiment mainly diagrammatically in which: 
       FIG. 1  is a side view of a manipulator including a test head; 
       FIG. 2   a  is a front view of the manipulator as shown in  FIG. 1 ; 
       FIG. 2   b  is a front view as shown in  FIG. 2   a , but with the test head removed; 
       FIG. 3  is a split rear view of the manipulator as shown in  FIG. 1 ; 
       FIG. 4   a  is a plan view of the manipulator as shown in  FIG. 1 , showing the positioning means in a first position; 
       FIG. 4   b  is a plan view as shown in  FIG. 4   a,  showing the positioning means in a second position; 
       FIG. 4   c  is a plan view as shown in  FIG. 4   a,  showing the positioning means in a third position; 
       FIG. 4   d  is a plan view as shown in  FIG. 4   a,  showing the positioning means in a fourth position. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The manipulator as shown in  FIGS. 1  to  3  serves to position a test head  40  on a device handler (not shown) for example for ICs or wafers. For this purpose, the manipulator comprises a column  10  composed of two upright posts  11   a  and  11   b  spaced away from each other. The column  10  is arranged on a rotational plate  50  which is secured to a bedplate  60 . By means of the rotational plate  50  the column  10  is rotatable about its vertical axis. Depending on the particular application, the rotational plate  50  may also be additionally guided on rails secured to the bedplate  60  to ensure maximum possible positioning of the column  10  in its entirety. 
   Arranged on each upright post  11   a,    11   b  of the column  10  is a linear guide  12   a,    12   b  respectively by means of which a slave actuator  13  clasping two opposing outer faces  15   a,    15   b  of the upright posts  11   a,    11   b  can be travelled along the column  10  vertically. In this arrangement, the slave actuator  13  may be powered manually, hydraulically and/or pneumatically or electrically. In the latter case, the linear guides  12   a,    12   b  are expediently components of a linear motor. By means of an arresting lever  16 a the slave actuator  13  can be locked in each position. 
   Referring now to  FIG. 1  there is illustrated in particular how positioning means  20  are arranged on the slave actuator  13  for travelling in the horizontal plane. The positioning means  20  comprise articulated arms  21   a,    22   a,    22   b  disposed in pairs one above the other. Each of the articulated arms  21   a,    22   a,    22   b  is hinged at one end to a mount  31  and connected by its other end to the carriages  23   a,    23   b . Assigned to the carriages  23   a,    23   b  are guides  14   a,    14   b  by means of which the carriages  23   a,    23   b  can be travelled horizontally. The guides  14   a,    14   b  configured as linear guides are arranged on the slave actuator  13  for travelling each independently of the other. The carriages  23   a,    23   b  may be powered by known ways and means manually, pneumatically and/or hydraulically or electrically. When powered electrically the guides  14   a,    14   b  and the carriages  23   a,    23   b  are expediently components of a linear motor. In this case it is good practice in a kinematic inverse assembly to arrange the carriages  23   a,    23   b  on the slave actuator  13  and to connect the articulated arms  21   a,    22   a,    22   b  to the ends of the guides  14   a,    14   b . Each of the carriages  23   a,    23   b  can be locked in position by an arresting lever  26   a.    
   Each of the articulated arms  21   a,    22   a,    22   b  arranged pivotable about a vertical axis on the carriages  23   a,    23   b  and the mount  31  can be likewise locked in position. For this purpose at least one clamping plate  24   a  is provided on which an arresting lever  25   a  preferably configured as an eccentric gear is arranged and which locates the articulated arms  21   a,    22   a,    22   b  positively connected. 
   At its upper end the mount  31  comprises a horizontally extending transverse axis  32  on which pivot arms  36   a,    36   b  connected to the articulated arms  21   a,    22   a,    22   b  are hinged. Arranged at each lower end of the pivot arms  36   a,    36   b  is an adjustable spacer  33   a  for precisely setting the inclination of the pivot arms  36   a,    36   b  relative to a holder  30  secured to the mount  31  for the test head  40 . 
   The holder  30  is arranged by means of pivot bearing  35  on the side of the mount  31  opposite the pivot arms  36   a,    36   b . The pivot bearing  35  permits rotation of the substantially bifurcated holder  30  about its longitudinal centerline extending in the y direction. In addition, the test head  40  is arranged on the holder  30  for pivoting about an axis of rotation  41  extending horizontally in the y direction so that a face  42  of the test head  40  is able to assume any position three-dimensionally. The holder  30  and the mount  31  are provided with a through-passage  34 , as is particularly evident from  FIG. 2   b . The through-passage  34  serves to receive the cable assembly of the test head  40  for leading it out between the upright posts  11   a,    11   b.    
   Referring now to  FIG. 3  there is illustrated in particular how the slave actuator  13  is connected to a counterweight  73  by a belt  72  guided over a pulley  71  at the upper end of the column  10 . The counterweight assembly  70  formed in this way serves to compensate the load on the positioning means  20  caused by the, as a rule, relatively heavy weight of the test head  40  by known ways and means. To make for balanced loading, the counterweight  73  is split in two parts, each of which moves within the upright posts  11   a,    11   b.    
   The manipulator as described above is characterized by precise repeatability in smooth motion of the test head  40 . The reason for this is the ability to position the slave actuator  13  vertically in the z direction. In addition to this the test head  40  can be reproducibly positioned in the horizontal plane by the articulated arms  21   a,    22   a,    22   b  and carriages  23   a,    23   b . Referring now to  FIGS. 4   a  to  4   d  there are illustrated various positions of the positioning means  20 . In  FIG. 4   a  the positioning means  20  are in a home position, i.e. the carriages  23   a,    23   b  are retracted on the slave actuator  13  and the articulated arms  21   a,    22   a,    22   b  are parked in a position parallel to the carriages  23   a,    23   b . In  FIG. 4   b  the positioning means  20  are positioned for linear travel relative to the test head  40 , i.e. the position of the articulated arms  21   a,    22   a,    22   b  is unchanged but the carriages  23   a,    23   b  are travelled somewhat further in the y direction. 
   Referring now to  FIG. 4   c  there is illustrated the positioning means  20  positioned so that although the test head  40  is pivoted in both the x direction and y direction, its face  42  always remains oriented parallel to the column  10 . To ensure shifting of the test head  40  exclusively in the x direction, the shift in the y direction prompted by pivoting the articulated arms  21   a,    22   a,    22   b  can be compensated by a corresponding shift in the movement of the carriages  23   a,    23   b.    
   Referring now to  FIG. 4   d  there is illustrated another positions of moving the test head  40  by the positioning means  20  showing the carriages  23   a,    23   b  each positioned independently of the other differingly far from the home position as shown in  FIG. 4   a . It is in this way that the articulated arms  21   a,    22   a,    22   b  are pivoted such that the test head  40  is rotated relative to its starting position as shown in  FIG. 4   a . In the position as shown in  FIG. 4   d  the face  42  of the test head  40  is oriented inclined to, for instance, the side of the slave actuator  13  opposing the test head  40 . Rotation of the test head  40  solely by the positioning means  20  can be combined with rotation of the column  10  by the rotational plate  50  for speedy, convenient movement of the test head  40  into any position three-dimensionally. 
   The manipulator as described above is characterized in addition by a simple and compact configuration. This is primarily due to splitting the column  10  into two upright posts  11   a,    11   b  spaced away from each other since this now makes it possible to route the cable assembly of the test head  40  through the through-passage  34  without kinking between the two upright posts  11   a,    11   b . The spacing of the upright posts  11   a,    11   b  from each other is expediently selected as a function of the thickness of the cable assembly. It is in addition useful to arrange the upright posts  11   a,    11   b  symmetrically on the rotational plate  50  for kinkless cable routing. Furthermore, the pivot arms  36  of the mount  31  permit precise orientation of the holder  30  relative to the positioning means  20  which due to the relatively heavy weight of the test head  40  in general are subjected to quite considerable flexural loading. Last but not least, providing the counterweight assembly  70  makes for comparatively smooth positioning of the positioning means  20 . 
   LIST OF REFERENCE NUMERALS 
   
       
         10  column 
         11   a  upright post 
         11   b  upright post 
         12   a  linear guide 
         12   b  linear guide 
         13  slave actuator 
         14   a  guide 
         14   b  guide 
         15   a  outer face 
         15   b  outer face 
         16   a  arresting lever 
         20  positioning means 
         21   a  articulated arm 
         22   a  articulated arm 
         22   b  articulated arm 
         23   a  carriage 
         23   b  carriage 
         24   a  clamping plate 
         25   a  arresting lever 
         26   a  arresting lever 
         30  holder 
         31  mount 
         32  transverse axis 
         33   a  spacer 
         34  through-passage 
         35  pivot bearing 
         36   a  pivot arm 
         36   b  pivot arm 
         40  test head 
         41  axis of rotation 
         42  surface 
         50  rotational plate 
         60  bedplate 
         70  counterweight assembly 
         71  pulley 
         72  belt 
         73  counterweight 
       x coordinate 
       y coordinate 
       z coordinate

Technology Category: 7