Browse Prior Art Database

Determining Circuit Card Mapping Points for a Probing System

IP.com Disclosure Number: IPCOM000118745D
Original Publication Date: 1997-Jun-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 96K

Publishing Venue

IBM

Related People

Lo, J-C: AUTHOR [+3]

Abstract

Disclosed is a method for automatically determining the height mapping points for a specific type of circuit card to be measured within a high-speed probing system. The coordinates of these points determine where height measurements are subsequently made on each circuit card of this type at the beginning of circuit testing. Such measurements provide a map representing the height of the surface an individual circuit card relative to the test probe, allowing fast and accurate probing operations while preventing probe damage.

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

Determining Circuit Card Mapping Points for a Probing System

      Disclosed is a method for automatically determining the height
mapping points for a specific type of circuit card to be measured
within a high-speed probing system.  The coordinates of these points
determine where height measurements are subsequently made on each
circuit card of this type at the beginning of circuit testing.  Such
measurements provide a map representing the height of the surface an
individual circuit card relative to the test probe, allowing fast and
accurate probing operations while preventing probe damage.

      High-speed probing systems depend upon the use of precise,
short-stroke z-axis actuators, which in turn make it necessary to
generate a height map of an individual circuit card being tested.
Such a map is generated by sending a probe to specific locations at
which a 'touch' procedure is used to find the local surface height of
the card.  The data obtained in this way is typically used to
generate a number of surface planes approximating the surface of
circuit card sagging under its own weight when it is loaded
horizontally into a circuit tester.  A minimum of three points is
used to determine the location of a single plane.

      The Flow Chart demonstrates the method.  After starting in
block 1, a routine calculates theoretical locations for points at
which measurements are to be made in block 2.  These calculations are
based on the size and shape of the card to be tested and on operator
inputs, which may, for example, provide an indication of the number
of points to be tested.  Next, in block 3, the routine selects one of
these theoretical locations to begin processing.

      Since the subsequent process of probing to establish data for
the height map relies simply on physical contact, probing can occur
within a feature of the circuit, such as a conductive circuit pad or
on an insulative portion of the card surface.  However, many cards
include surface discontinuities, such as holes or cut-outs, which can
cause inaccurate readings and even probe damage if they are probed
during this process.  The snap-to-feature option of the current
method prevents such mishaps by allowing the mapping points to be
placed only within rectangular circuit features, in which holes are
not present.

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