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Browse Prior Art Database

Determining Sample Alignment Points for a Probing System

IP.com Disclosure Number: IPCOM000118696D
Original Publication Date: 1997-May-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 92K

Publishing Venue

IBM

Related People

Nemethy, AN: AUTHOR

Abstract

Disclosed is a method for automatically determining alignment points for a specific type of circuit card to be measured within a high-speed probing system. These alignment points may be chosen from a number of visible features, such as circuit pads, on the surface of the card. These points are subsequently used to determine the registration of the circuit printed on each such circuit card with respect to the probing system measuring the circuit. The high-speed probing system includes a television-type camera and associated logic, capable of recognizing such visible features.

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

Determining Sample Alignment Points for a Probing System

      Disclosed is a method for automatically determining alignment
points for a specific type of circuit card to be measured within a
high-speed probing system.  These alignment points may be chosen from
a number of visible features, such as circuit pads, on the surface of
the card.  These points are subsequently used to determine the
registration of the circuit printed on each such circuit card with
respect to the probing system measuring the circuit.  The high-speed
probing system includes a television-type camera and associated
logic, capable of recognizing such visible features.

      The Figure is a flow chart showing this method, in which
features are selected from a list of all features present in a layout
of the circuit to be tested.  After the process is started in block
1, a determination is made in block 2 of the boundaries of each
region to be used.  Since this method provides a single alignment
point for each region, this determination is based on such factors as
the overall  size and shape of the circuit card and information
provided by the user  regarding the number of alignment points
desired.

      In block 3, a first feature is selected from the list of
circuit features.  If this feature is within the region being
examined, as determined in block 4, data representing the feature is
added, in block 5, to a region table being developed for that region.
If the feature is not in the region, it is not added to the region
table. In  either case, a determination is made in block 6 of whether
the feature  being examined is the last feature in the list of
circuit features. If  it is not, the system advances in block 7 to
examine the next feature in  block 4.

      If the feature being evaluated is the last feature in the list
of circuit features, as determined in block 6, it is known that all
of the possible features have been added to the region table.  At
this time, in block 8, since it is desirable to locate the circuit by
means of points as close as possible to the corners of the card, the
features in the region table are sorted according to an ascending
order of the sum of their x- and y-coordinates providing distances
from the nearest such corner.

      Ne...