[SI-LIST] Re: ESD is a low frequency event -really??
- From: Chris Cheng <Chris.Cheng@xxxxxxxxxxxx>
- To: "'khayden@xxxxxxxxxxxxxxxxxx'" <khayden@xxxxxxxxxxxxxxxxxx>,si-list@xxxxxxxxxxxxx
- Date: Fri, 5 Mar 2004 13:58:08 -0800
Bingo.
I've seen a large enterprise class server under contact ESD test being taken
down by a single zap.
The problem was traced back to the isolated chassis and logic ground. If you
zap it in the right place, the discharge is going through the metal can of
the oscillator in the middle of the master clock board. The crystals inside
doesn't like the voltage disturbance and the clock goes away. It is really
awesome to see all those blinking LEDs on the refrigerator size server go
south in an instant when you zap it with the ESD gun. Makes you feel like a
superman.
ESD test, copper tapes, cutting fingers, pain....ouch ouch ouch
-----Original Message-----
From: Ken Hayden [mailto:khayden@xxxxxxxxxxxxxxxxxx]
Sent: Friday, March 05, 2004 9:45 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: ESD is a low frequency event -really??
I would just like to add that although an electrostatic discharge to a front
panel or chassis part will very likely be diverted around circuitry such
that it
causes no permanent damage, there is still the likelihood of upsetting
signals.
Are we only discussing physical damage in this thread, or "soft" circuit
malfunction as well? If we are concerned about preventing a single-bit
serial
communication error, for example, we must take additional precautions.
Ken Hayden
Integral Access, Inc.
Julian Ferry wrote:
> I suspect we are dealing with a communication problem here. Most everyone
> understands that there are high frequency components in ESD events. There
> are plenty of real world experiences to help illustrate that (spark gap
> radios, relay noise, spark plug noise in car radios, etc).
>
> But knowing Lee's background as a fix it/prevent it kind of guy, I think
> what he meant to say is that ESD damage can be prevented by treating ESD
as
> if it were a low frequency event. The high frequency components are
there,
> but you probably don't need to waste your time worrying about them. As
> others have hinted, they either don't have the energy required to do much
> damage, and/or, they dissipate or find their way to ground with out the
need
> for human intervention.
>
> Maybe this is were the discussion should focus (if there is any further
> discussion).
>
> Am I correct, Lee?
>
> Julian Ferry
> High Speed Engineering Manager
> Samtec, Inc.
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On
> Behalf Of Richard Schumacher
> Sent: Friday, March 05, 2004 10:15 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: ESD is a low frequency event -really??
>
> ESD can indeed have very high frequency components. How does that
> invalidate Lee's advice against the wholesale addition of _DC_
> connections between logic ground and chassis at multiple points?
>
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