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Browse Prior Art Database

Algorithm to Detect Soldering Defects Due to Lifted Lead

IP.com Disclosure Number: IPCOM000121540D
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Nakano, H: AUTHOR

Abstract

This article describes an apparatus and an algorithm to detect soldering defects of surface mount components due to lifted lead. The apparatus features the use of oblique two cameras above the printed circuit board and lighting devices below the cameras. The algorithm features rule-based defect judgement based upon four areas of interest in two images captured by the two cameras.

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Algorithm to Detect Soldering Defects Due to Lifted Lead

      This article describes an apparatus and an algorithm to
detect soldering defects of surface mount components due to lifted
lead.  The apparatus features the use of oblique two cameras above
the printed circuit board and lighting devices below the cameras.
The algorithm features rule-based defect judgement based upon four
areas of interest in two images captured by the two cameras.

      Two images are captured by the following sequence (Fig. 1):
   1. Turn on light 1.
   2. Capture image by using camera 1.
   3. Turn off light 1 and turn on light 2.
   4. Capture image by using camera 2.

      Camera 1 views one side of the lead, and camera 2 views the
other side of the lead.  Two windows (area of interest) are set for
each of the images.  Windows 11 and 12 are set for image 1, and
windows 21 and 22 are set for image 2.  The windows 11 and 21 are
set to include substrate regions adjacent to the lead ends and the
windows 12 and 22 are set to include lead foot portions (Fig. 2).

      Lifted lead has thick solder between the lead and substrate
which results in a larger bright portion in the image than that for
good lead.  Also, lifted lead tends to cause solder to spread over
beyond the lead end.  In each of the windows, the number of pixels
which are brighter than a predetermined threshold are counted.  The
value is called "feature value" herein.  By using four feature values
ob...