Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Automatic CCTV Positioning System

IP.com Disclosure Number: IPCOM000076106D
Original Publication Date: 1972-Jan-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 59K

Publishing Venue

IBM

Related People

Duffy, RF: AUTHOR [+3]

Abstract

The placement of semiconductor chips on studs and the subsequent positioning of collars and probes for connection to the chip, requires that the chips be positioned to within +/- 0.5 mils and oriented to within 0.3 degrees. Due to inaccuracies of the mechanical portions of the positioning system, the allowed tolerance for determining the position of the chips relative to its coordinate axis is +/- 0.2 mils.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 50% of the total text.

Page 1 of 3

Automatic CCTV Positioning System

The placement of semiconductor chips on studs and the subsequent positioning of collars and probes for connection to the chip, requires that the chips be positioned to within +/- 0.5 mils and oriented to within 0.3 degrees. Due to inaccuracies of the mechanical portions of the positioning system, the allowed tolerance for determining the position of the chips relative to its coordinate axis is +/- 0.2 mils.

In the present system, shown in Fig. A, a closed-circuit television (CCTV) camera 2 scans the corner solder pads of chip 3 to determine its position and orientation with respect to mounting stud 5. Positioning to within +/- 0.2 mils is accomplished by an x-y-theta table 22 having a stud holder 18 rigidly mounted thereon. A rigid tower 6 holds an illuminating lamp 7, TV camera 2, and assorted optical elements for focusing the light from the lamp on chip 3, and returning light reflected from the chip to a vidicon tube 9 in the TV camera head. The output from the TV camera is fed to a camera control unit 10, then to an interface unit 12 and a video preprocessor 14 which routes the information collected to a digital computer 15. The computer is programmed to calculate the position of the chip relative to the positioning table, by employing timing data obtained from the TV raster.

The raster is highly stable and accurate, its stability being assured by a highly stable oscillator 30 in interface unit 12. The oscillator provides clock pulses used to digitally control the sweep and deflection circuits of control unit 10 by triggering each TV line, field, and frame with little or no variation. Counters in video preprocessor 14 determine where individual TV lines in the raster cross selected solder pads, by noting the time of crossing relative to the start of the raster. The times of crossing are used to compute pad position in computer 15. About 30 TV lines in the raster, each about 0.2 mils wide, will straddle the solder pad. Each line consists of about 600 elements and about 27 consecutive elements along the line, each about 0.19 mils long. The use of many TV lines and elements along a TV line permits estimation of center of the pad to better than one TV line in one direction, say the y direction, and better than one element along a line in the x direction.

The center of each solder pad is computed by calculating the center from the end-points of the TV lines which cross the pads. The horizontal and vertical drive lines from the camera control unit 10 reset the counters in preprocessor 14.

The computer directs servo control 17 which drives servo motors 16 to control positioning table 22 in well-known fashion. Position feedback information from the positioning table permits stud 5 to be located under the chip and oriented properly.

The principal phenomenon which allows the present system to operate with unprecedented accuracy is the very poor reflectivity of the solder pads as compared to the chip subs...