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Probe Collision Avoidance Procedure for Parametric Testers

IP.com Disclosure Number: IPCOM000099518D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 5 page(s) / 160K

Publishing Venue

IBM

Related People

Freisitzer, N: AUTHOR [+2]

Abstract

A technique is described whereby a software procedure is used in equipment for the testing of circuit parameters of multi-level ceramic (MLC) substrates. An algorithm provides a means of eliminating the possibility of test probes collisions during the test. The procedure consists of two parts: Collision detection during end-point selection and collision prevention during probe positioning.

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Probe Collision Avoidance Procedure for Parametric Testers

       A technique is described whereby a software procedure is
used in equipment for the testing of circuit parameters of
multi-level ceramic (MLC) substrates.  An algorithm provides a means
of eliminating the possibility of test probes collisions during the
test.  The procedure consists of two parts:  Collision detection
during end-point selection and collision prevention during probe
positioning.

      Two probe types were required for the parametric tester for
which these collision avoidance algorithms were created: a
stationary, single-tipped probe used for continuity testing, as shown
in Fig. 1 (a) and a rotating, three-tipped probe for impedance
testing, as shown in Fig. 1 (b).  Of the two probe types, the
rotating impedance probes are especially sensitive to physical
contact. Therefore, this description of the concept focuses on the
algorithms which prevent collision of the more sensitive impedance
probes.

      To perform a continuity test of a circuit, single-tip probes
are applied to the end points of the circuit.  For the purpose of
collision avoidance, the geometry of these probes is approximated by
a circle with a radius equal to the probe's diameter plus a safety
delta and consists of a single point/circle with a predetermined
radius, as shown in Fig. 2.  Since the probe tip extends far beyond
the probe's super- structure, the collision avoidance procedure for
this probe type considers only the center of the probe tip and its
radius.

      To perform an impedance test of a circuit, three-tipped probes
(one signal probe, two ground probes) are applied to the end points
of the circuit.  In this case, the signal probe contacts a signal
point, and one of the ground probes contacts an available ground
point.  Two ground probes are provided, as shown in Fig. 3, to
increase the likelihood of finding a ground point at one of the two
radii from the signal probe.  The ground point's location with
respect to the signal point determines the required rotation of the
impedance probe.

      The first part of the collision avoidance procedure is to
eliminate test points which would cause probe collisions
(interference), during the test point selection process, before tests
are executed.
    Interference can consist of the following types:
    Probe with probe interference - where the probes themselves would
physically contact.

      Probe with structure interference - where one or both of the
probes would physically contact the adjacent probe's super structure.

      Structure with structure interference - where the probes'
superstructures would physically contact.

      Probe with structure interference is the simpler case of
determining area intersections for the fixed superstructure
geometrics.  The probe's geometry is helpful in minimizing the code
involved.  For rotating probes, the more complex case of probe/probe
interfer...