Browse Prior Art Database

Electrical Antenna Detection to Prevent Intermittent Timing Failures

IP.com Disclosure Number: IPCOM000109626D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 126K

Publishing Venue

IBM

Related People

Basile, JE: AUTHOR [+2]

Abstract

When Engineering Changes (ECs) or Temporary Fixes (TXs) are applied to existing hardware, all printed wire connections can not always be deleted. In some cases, all pins in a net are not ECable or deletable. For example, a subset of pins on each Hercules chip site are ECable. The rest are not accessible via top surface actions. Other modules have package I/Os that are not all ECable.

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Electrical Antenna Detection to Prevent Intermittent Timing Failures

       When Engineering Changes (ECs) or Temporary Fixes (TXs)
are applied to existing hardware, all printed wire connections can
not always be deleted.  In some cases, all pins in a net are not
ECable or deletable.  For example, a subset of pins on each Hercules
chip site are ECable.  The rest are not accessible via top surface
actions.  Other modules have package I/Os that are not all ECable.

      In Fig. 1, an original build net is shown with four chip pins.
Three of the chip pins are ECable via top surface delete pads.  The
fourth is not.  Contrast this with Fig. 2 in which the net has been
ECed by swapping the ordering of the third and fourth pins.  Note the
large and complex antenna that has been created.

      In general, when a net is ECed or TXed, a full net strip is
performed.  The full net strip process disconnects all printed
connections from all pins in the net.  Since some pins are not
ECable, full net strip is not always possible.  When it is possible,
all connections are made with EC lines on the top surface and no
antennas are generated.

      Antennas can cause signal noise which can be a serious problem.
Since antennas cause reflections that can be significant, they have
the potential of causing noise on quiet lines.  If the net's noise
margin is breached by these reflections, false switching may occur as
a result, causing a potential hard failure in the processor.

      Without a process to isolate antennas you do not know which
hardware is valid and which hardware is scrap (with respect to
antennas) prior to it arriving at the test floor.  Your options
include scrapping all suspect hardware, including hardware with
anten...