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# Image Processing Algorithm to Locate Solder Joints

IP.com Disclosure Number: IPCOM000121218D
Original Publication Date: 1991-Aug-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 63K

IBM

## Related People

Fujita, T: AUTHOR [+2]

## Abstract

This article describes apparatus and algorithm for determining the coordinates of lead edges of flat package IC soldered on printed circuit board. The apparatus features the use of two oblique cameras above the printed circuit board and lighting devices below the cameras. The algorithm features that the camera settled at the front side of the leads determines the x-coordinate of the lead edge, and another settled at the back side of the leads determines the y-coordinate.

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Image Processing Algorithm to Locate Solder Joints

determining the coordinates of lead edges of flat package IC soldered
on printed circuit board.  The apparatus features the use of two
oblique cameras above the printed circuit board and lighting devices
below the cameras.  The algorithm features that the camera settled at
the front side of the leads determines the x-coordinate of the lead
edge, and another settled at the back side of the leads determines
the y-coordinate.

The image of leads is captured by two cameras after the
lighting devices are turned on (see the figure).  In the image
captured by the front side camera 1, the knee position or bent
portion of the lead shines brightly.  By using the image, the
x-coordinate of the center of each lead can be determined.  In the
image captured by the back side camera 2, flat area of the lead
around the knee position shines brightly.  By using the image, the
boundary between the lead and dark package can be determined.  If the
lead length is known, the y-coordinate of the lead edge can be
determined.

To determine the x-coordinate of the lead, the following
operations are performed on the image captured by the front side
camera 1.
1. Set an area of interest around the knee position of the lead.
2. Perform projection (summing of gray level of each pixel) along
the y-axis, i.e., the longitudinal direction of the lead.
3. Perform avera...