Since latent defects are parametric changes that cannot be detected using
current technology, to prove cumulative damage is basically impossible.
 Logically, many ESD catastrophic failures are due from one discharge while
others are due to a number of discharges.

Per ESD Handbook TR20.20 section 2.7 Types and Causes
"Electrostatic damage to electronic devices can occur at any point, from
the manufacture of the device to field service of systems. Damage results
from handling the devices in uncontrolled surroundings or when poor ESD
control practices are used. Generally damage can manifest
itself as a catastrophic failure, parametric change or undetected
parametric change (latent defect)."

Per ESD Handbook TR20.20 section 2.7.2 Latent Defects
"A device that is exposed to an ESD event may be partially degraded, yet
continue to perform its intended function. However, the operating life of
the device may be reduced dramatically. A product or system incorporating
devices with latent defects may experience a premature failure after the
user places them in service. Such failures are usually costly to repair and
in some applications may create personnel hazards.  It is easy with the
proper equipment to confirm that a device has experienced catastrophic
failure or that a part is degraded or fails test parameters. Basic
performance tests will substantiate device damage.

However, latent defects are virtually impossible to prove or detect using
current technology, especially after the device is assembled into a
finished product.  Some studies claim that the number of devices shipped to
users with latent defects exceeds the number that fail catastrophically due
to ESD in manufacturing. Other studies exist that claim that no failure
mechanism exists to prove the existence of latent failures. To date, most
studies contradict one another as to what magnitude of ESD damage can be
attributed to latency. ESD damage is usually caused by one of three events:
??Electrostatic Discharge to the device.
??Electrostatic Discharge from the device.
??Field Induced discharges."

Gene Felder
[log in to unmask]



-----Original Message-----
From:   Ingemar Hernefjord (KC/EMW) [SMTP:[log in to unmask]]
Sent:   Tuesday, October 07, 2003 11:43 PM
To:     [log in to unmask]
Subject:        Re: [TN] Cumulative damage from ESD

 << File: ATT00008.htm >> If that was true, we have spent millions of
dollars in vain to protect GaAs devices from ESD. An electrostatic high
voltage charge injection , much energy or little, is never welcome. A grain
falling onto your head may not be observed by you, not a second one either,
but if the grain becomes a coconut, you'll probably get shorter lifetime.
How do you know what is a damage causing ESD or what is a harmless? Would
never risk anything else than full ESD protection. What was in their heads
1988?
Ingemar Hernefjord
Ericsson Microwave Systems
-----Original Message-----
From: Alex Krstic [mailto:[log in to unmask]]
Sent: den 3 oktober 2003 00:45
To: [log in to unmask]
Subject: [TN] Cumulative damage from ESD




Hi all.  Simple question yet I haven't read the definitive answer.  Is
damage from ESD cumulative?  Reason I ask is the following statement I came
across in a GaAs MMIC article.

"Other studies have also concluded that damage from repeated exposure to an
ESD level is not cumulative and that noncatastrophic damage does not
degrade device lifetime."  The statement references the EOS/ESD Symposium
Proceedings 1988.

I've always preached that ESD damage is cumulative.

Alex "Shocked" Krstic
NovAtel Inc.


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