Browse Prior Art Database

Void And Island False Call Limiter

IP.com Disclosure Number: IPCOM000102086D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 3 page(s) / 95K

Publishing Venue

IBM

Related People

Forslund, DC: AUTHOR

Abstract

When morphology is employed in image processing of inspection images of printed circuit boards, the technique of contracting the image a fixed number of times is used to determine the defect of a violation of signal line width. This technique gives rise to false defect calls when cosmetic voids are present within the line under inspection. The circuit described provides a means to desensitize the usual algorithmic circuitry to the morphological response to these artifacts.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Void And Island False Call Limiter

       When morphology is employed in image processing of
inspection images of printed circuit boards, the technique of
contracting the image a fixed number of times is used to determine
the defect of a violation of signal line width. This technique gives
rise to false defect calls when cosmetic voids are present within the
line under inspection. The circuit described provides a means to
desensitize the usual algorithmic circuitry to the morphological
response to these artifacts.

      While this circuit is described for voids in conductive paths
with the focus toward measuring cross-sectional conductive path in
image pixel count, the circuit operating on the inverse original
image and providing positive image at the output, can provide false
call limiting of conductive islands material located between signal
lines.  This is useful when a series of near shorting islands has an
effective but acceptable potential high resistance shorting path.

      Fig. 1A illustrates a typical PCB signal line with a wide and a
narrow mousebite, and two internal voids.  In this example, it is
assumed that the conductive path must be at least three pixels wide.
It is obvious that the two mousebites restrict the conductive path to
two pixels and, therefore, the algorithm should flag these as
defects.  One internal void is situated between two conductive paths
of two pixels each and, therefore, should not be called out as a
defect.  The other internal void is situated such that the
cross-sectional pixel count ranges from three to four and back to
three.  However, the two conductive paths, each have a pinch point of
one conductive pixel, and therefore the void should be called as a
defect.

      Fig. 1B illustrates the result of the typical contracti...