Browse Prior Art Database

Short-Circuit Detection Method for Circuit Boards

IP.com Disclosure Number: IPCOM000106101D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

Huynh, D: AUTHOR [+2]

Abstract

Described is a hardware implementation for detecting power/ground shorts on assembled circuit boards by using passive liquid crystal films to detect shorts. The method reduces the need for specialized test instrumentation.

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This is the abbreviated version, containing approximately 52% of the total text.

Short-Circuit Detection Method for Circuit Boards

      Described is a hardware implementation for detecting
power/ground shorts on assembled circuit boards by using passive
liquid crystal films to detect shorts.  The method reduces the need
for specialized test instrumentation.

      In prior art, the detection of short circuits between power and
ground planes of assembled printed circuit boards involved the
localizing of the short by means of infrared imaging instrumentation
that was capable of detecting hot-spots on the circuit card.
Although the prior art infrared method was effective in locating the
shorts, the method involved the use of expensive specialized test
instrumentation.  The concept described herein operates similarly to
the prior art infrared approach for localizing the shorts, but
without the need for expensive instrumentation.

      It is known that passive liquid crystal films respond to
temperature differences by changing the polarization angle of the
film throughout the area of the temperature gradient.  The change in
polarization angle due to temperature changes results in a change of
color and shading of the film.  Existing commercial applications of
the film have been used in color changing thermometers, science
demonstrations and novelty items.  Typically, the different film
chemistry results in different temperature ranges.  By using this
color change with temperature, the application of passive liquid
crystal films for localizing detecting shorts has been proven to be
effective.

     ...