Patent GB-1118528-A (GB)
Title: Positioning apparatus
IPC: G03F9/00
Filed: 1966-12-02
Abstract: 1,118,528. Photo-electric position finding. INTERNATIONAL BUSINESS MACHINES CORP. 2 Dec., 1966 [13 Dec., 1965], No. 53969/66. Heading H4D. In apparatus for positioning an object which carries at least one mark, sensing means scans the object along rectilinear lines to give a signal when the mark is sensed and the signal controls movement of the object to a selected location corresponding to a selected line in which the mark is sensed. In the embodiment the sensing means is photo-electric and terminal pads 41 . . 44 afford positioning in X and Y directions and rotational positioning, by respective motors 24, 25 and 26, the object being an electronic circuit chip 20. Microscope objective 31 images light reflected from the chip on to a vidicon 36 having X and Y deflexion coils 46, 48 for producing scanning lines 50 . . . 61. Chip 20 is shown in Fig. 2 in the desired position whereby scan line 60 crosses pads 41 and 43 but, if not, the chip is incremented downwardly until scan line 60 (the scans being made after each incremental movement) crosses pad 41 or 43 the chip being rotated if only one pad is sensed. The process continues until both pads are sensed along line 60. Y deflexion current is then adjusted to give a scan along line 61 to check whether either pad has dropped too much. If no pad is sensed on line 61, X alignment is begun by scan lines 50 to 59 in succession, no pads being sensed until line 54 when the chip is correctly positioned. Assuming the chip off-set to the left such that line 51 intercepts pads 41, 42, the scan line shifts and the sensing signal on line 64, Fig. 1A, causes the chip to move to the right in decreasing steps; when the pads are sensed along line 54 a scan is taken along line 53 for a check; if no pads are sensed, chip positioning is completed. where the chip is offset to the right, scan lines 55 to 59 are utilized in conjunction with pads 43, 44. Control system, Fig. 1B. System synchronization is afforded by clock pulses at terminal 80. Initially, gate 82 is conditioned to pass clock pulses to a line 90 for Y and rotational positioning; the first clock pulse triggers sawtooth generator 92 for horizontal deflexion amplifier 98 to give scan line 60, Fig. 2, the line position in the Y direction being obtained from a source 104. If no pads are sensed a delayed clock pulse (after the scan is completed) advances motor 24. The second clock pulse repeats the same scan line and if no pads are sensed motor 24 advances a further increment, the sequence continuing until one of pads 41, 43 is sensed, a pulse on line 117 actuating a single-shot multivibrator to remove a signal from lead 114 for a period long enough to interrupt the passage of the pulse from delay 113 to motor 24. Gates 131, 132 control the direction of chip rotation until both pads 41, 43 are sensed during the same clock pulse cycle, as detected by a gate 143 and a single-shot multivibrator 145 thereby supplying a new voltage from source 105 to cause the next scan to be along line 61. The next clock pulse on lead 90 initiates that scan; if either pad 41 or 43 has dropped too low a gate 133 terminates operations or causes, by means not shown, upward movement of the chip in preparation for a new attempt at alignment. If no pads are sensed along line 61, the next series of clock pulses at terminal 80 are routed to lead 154 to carry out the X positioning the stepping of the Y-direction scan lines in the X-direction utilizing a binary counter 162.