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# Method for Detecting Position of Chip Solder Ball Array

IP.com Disclosure Number: IPCOM000120977D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 88K

IBM

## Related People

Saitoh, F: AUTHOR

## Abstract

Disclosed is a method for detecting the position of a solder ball array located on the bottom of a chip by image processing. The algorithm is applicable regardless of the pattern and size of the array. STEP 1: DETECTION OF GRAVITATIONAL CENTER

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Method for Detecting Position of Chip Solder Ball Array

Disclosed is a method for detecting the position of a
solder ball array located on the bottom of a chip by image
processing.  The algorithm is applicable regardless of the pattern
and size of the array.
STEP 1:  DETECTION OF GRAVITATIONAL CENTER

The gravitational center is detected in the gray image which
includes the solder ball array.  It may be off the actual center of
the array a little.  But the distance between the gravitational
center and the actual center should preferably be less than the space
between adjacent solder balls.  The position of the gravitational
center is used as a basic position for the following processes.
STEP 2:   DETECTION OF ROTATION ANGLE AND POSITION OF ARRAY

Fig. 1 shows a method for detecting the position of the array
and its slant or rotation angle.  A vertical line which goes through
the gravitational center is drawn.  All the gray level values of
picture elements located on the line are added and its result is
stored.  Then the line is rotated slightly about the gravitational
center, the sum for the rotated line is again calculated and stored.
The operation is repeated while rotating the line to scan in a
predetermined angle range, and the angle of the line which gives the
maximum sum is determined and stored.

Next, the gravitational center or basic position is moved to
the left or right slightly and the above operations are repeated.
T...