Browse Prior Art Database

Optical Method for Detecting Wires Touching a Surface

IP.com Disclosure Number: IPCOM000109601D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 92K

Publishing Venue

IBM

Related People

Brecher, VH: AUTHOR [+3]

Abstract

Disclosed is a method for determining whether thin wires are touching a nearby surface. In certain manufacturing processes, thin wires (mils in diameter, for example) have to cross flat regions without touching them. Inspection to assure there is no contact is difficult, as the images are two-dimensional, but the problem is to assure the wires are high enough up from the surface. The solution recommended here is to use a beam of light to illuminate the wire and surface combination from above and then either observe the shadow distance from the wire or, perhaps more rapid and giving greater visual stimulus, to move the surface parallel to itself, so that the wire shadow moves. The degree of motion, or its absence, should readily indicate whether the wire is touching the surface or not.

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Optical Method for Detecting Wires Touching a Surface

       Disclosed is a method for determining whether thin wires
are touching a nearby surface.  In certain manufacturing processes,
thin wires (mils in diameter, for example) have to cross flat regions
without touching them.  Inspection to assure there is no contact is
difficult, as the images are two-dimensional, but the problem is to
assure the wires are high enough up from the surface.  The solution
recommended here is to use a beam of light to illuminate the wire and
surface combination from above and then either observe the shadow
distance from the wire or, perhaps more rapid and giving greater
visual stimulus, to move the surface parallel to itself, so that the
wire shadow moves.  The degree of motion, or its absence, should
readily indicate whether the wire is touching the surface or not.

      A microlectronic package with wires going from various
locations was placed under a low-power (c. 10X) microscope.  A bright
light was directed at the product surface at an angle of about 45
degrees to the surface, producing an elliptical illuminated area
under the microscope objective.  The microscope objective was
directed at the illuminated spot at about a 45-degree angle, so that
the light reflected from the surface of the product reflected into
the microscope.  (Beam, illuminated spot, and microscope objective
were in the same plane.)  This made the background about as bright as
possible, accentuating...