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Browse Prior Art Database

Product Alignment Method for Probing Systems

IP.com Disclosure Number: IPCOM000115654D
Original Publication Date: 1995-Jun-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 148K

Publishing Venue

IBM

Related People

Boyette, J: AUTHOR [+3]

Abstract

Disclosed is an invention that describes an automated approach to achieving a high degree of accuracy when aligning a probing system with the device to be tested, utilizing a camera and vision system to automate the device alignment process.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 40% of the total text.

Product Alignment Method for Probing Systems

      Disclosed is an invention that describes an automated approach
to achieving a high degree of accuracy when aligning a probing system
with the device to be tested, utilizing a camera and vision system to
automate the device alignment process.

      Prior art, the alignment was accomplished using Hunt & Peck
technique that is slow, lacking in robustness, and destructive.

      Technical Background - Probing systems must be able to locate
the test points of a product.  These test points are usually given as
coordinates relative to some origin on the surface of the product.

      Probing systems require a means of locating the probes with
respect to test points on a device to be tested.  Device terminal or
test sites are usually described in industry by orthogonal coordinate
frames or grids.  Probes are usually positioned by orthogonal XY
positioning table with XY coordinate frames.  Regardless of the
coordinate frame types a transformation is required to relate these
two frames.  Yielding this transformation will be referred to as the
alignment process.

      Alignment is done each time a device is loaded into the tool
when the process and placement deviation is larger than the
structures to be probed.  A "hunt and peck" method may be used such
that the probe is moved and actuated while using sensing feedback to
identify the test site structures.  This process can be slow,
destructive, and lack robustness.  This disclosure describes a method
that utilizes a camera and vision system to automate the process of
device alignment.  Using a monitor and optics the procedure may be
accomplished manually so as to save the cost of the vision system.

      This invention was implemented on a two probe system that
provided two stacked XY cartesian stages each carrying a Z actuated
probe.  A camera is mounted at a fixed distance from the probe such
that the view is roughly parallel, and in the same direction, as the
actuating stroke of the probe.  The product surface is parallel to
the XY positioner.  A flat surface is provided coplanar to the device
to be probed such that probing the flat surface alters the appearance
of the surface.  The flat surface will be referred to as the
reference and the probe mark as the reference point.

      The following describes a two step alignment procedure.  The
first step provides the offset between the center of the field of
view of the camera and the probe tip.  The second step provides the
transformation that allows the camera to be centered on any test site
on the surface of the product.  The probe is positioned by noting the
camera position and adding the probe offset.  At the end of the
process a product coordinate can be used to position the camera or
probe over the desired site.

      The system XY positioner is moved such that an unused portion
of the reference is located in the field of view of the camera. ...