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Browse Prior Art Database

Method for Eliminating Common Defects from Capacitance Opens Shorts Data

IP.com Disclosure Number: IPCOM000115796D
Original Publication Date: 1995-Jun-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 74K

Publishing Venue

IBM

Related People

Boyette, J: AUTHOR [+2]

Abstract

Disclosed is an invention that, via a unique software algorithm, provides a means for identifying common capacitive defects in circuit boards.

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

Method for Eliminating Common Defects from Capacitance Opens Shorts
Data

      Disclosed is an invention that, via a unique software
algorithm, provides a means for identifying common capacitive defects
in circuit boards.

      Detection of defects in circuit boards can be identified
through the use of capacitive measurements.  These measurements are
made on a sampling of products to determine the normal and expected
value and deviation in measurements.  A significant deviation in the
expected value will then indicate the presence of a defect.
Typically it is desirable to take readings from several products in
an attempt to Learn empirically what this Mean value should be and to
characterize the deviation.  A problem exists when there is a common
defect in the sample data that results in the defect being learned as
a normal reading.

      Capacitive measurements are made on circuit boards, and more
generally interconnect devices, to identify opens and shorts.  In the
presence of shorts the capacitance will at least double and in the
presence of an open will at least be reduced by half.

      The manufacturing process by its very nature is controlled to
minimize process deviation.  A determination of characteristic
capacitance of the interconnect for each network is easily
established and is a good indication of the presence of a defect when
it changes.

      It is desirable to establish the normal capacitance reading by
taking measurements from several products.  This is a simple straight
forward way to establish the Mean expected value.  A problem arises
when a common short or open establishes a Mean value which is
constant among the products sampled and makes the defect look normal.
An additional procedure or method must be utilized to address this
case during the learn process.

There are two methods proposed that address each of the open and
short cases:
  1.  The way to identify the open condition is to verify that all
 ...