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October 2003

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Subject:
From:
Matthias Mansfeld <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 3 Oct 2003 11:48:56 +0200
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On 2 Oct 2003 at 16:44, Alex Krstic wrote:

>
>
> 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.
[...]
>
> I've always preached that ESD damage is cumulative.
>
> Alex "Shocked" Krstic
> NovAtel Inc.

I would say it depends. Usually I think we are on the safe side if we
assume it's cumulative unless the basic physics state there is no
degradation.

My favourtite example: Remember the big varistors in power supplies.
If the power line _has_ transients, the varistors _will_ degrade more
and more, until the leak current is high enough for incineration
(thus, industry began to make special varistors with incorporated
irreversible thermo fuse).

Other side, if you know your transients are short enough and energy
limited, you can live with suppressor diodes instead, please the _big
fat expensive_ ones, and they will not degrade unless your transients
exceed the maximum ratings. If they die, they don't die slowly by
unsoldering themselves or roasting your power supply slowly, they die
spectacularely and leaving usually with a rock solid short.

I would say the same conclusion can be made for any device. If the
construction can dissipate the energy of a discharge, I would assume
no cumulative damage (and there is the little difference between a
suppressor diode and a FET gate).

Regards
Matthias Mansfeld

--
Matthias Mansfeld Elektronik * Leiterplattenlayout, Bestueckung
Am Langhoelzl 11, 85540 Haar; Tel.: 089/4620 093-7, Fax: -8
Internet: http://www.mansfeld-elektronik.de
GPG http://www.mansfeld-elektronik.de/gnupgkey/mansfeld.asc

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