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May 2005

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Subject:
From:
"Van Beveren Richard (RBAU/MFE4)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Van Beveren Richard (RBAU/MFE4) <[log in to unmask]>
Date:
Mon, 9 May 2005 15:46:39 +1000
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Lots of info in ESD on the internet, for example, http://www.esda.org is not a bad place to start.

As suggested by others, it's easy to build up charges over 30,000 volts on plastics and damage to ESD sensitive components can occur at a fraction of this.  There are also a few ways to inflict damage by ESD: discharge to the device, discharge from the device and field induced charges that can then lead to an dangerous discharge.  Most component spec. sheets I've seen will specify different maximum voltages for these ESD 'events' types typically referred to as Human Body Model (HBM), Charged Device Model (CDM) and Machine Model (MM).

If no specs exist, I'd be very, very careful about relying on a certain charge not being able to jump a certain distance not only because environment conditions influence this so much but because you could still be damaging your parts without a 'zap' taking place, or inducing a charge that leads to a 'zap' down the line somewhere.  Of course, keeping in mind that by the time you see or hear a zap you've got thousands of volts....

Richard van Beveren
Robert Bosch (Australia) Pty Ltd


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Brooks,Bill
Sent: Saturday, 7 May 2005 1:07 AM
To: [log in to unmask]
Subject: [TN] FW: Static and break over voltage spacing standards?


I hope that someone on the forum may have a comment or two about this
subject... and can help John.

- Bill

-----Original Message-----
From: John Smith [mailto:[log in to unmask]]
Sent: Thursday, May 05, 2005 7:21 AM
To: 'Bill Brooks'
Subject: RE: Web site question

Thank you for your response Bill, I am trying find out at what voltage and
at what distance I need to be concerned about a static discharge from a
plastic surface. I have a silicon wafer processing tool and there is concern
about static discharge from the exterior plastic panels. I want to be able
to determine, the voltage vs.. distance safe point, i.e. (at 500v of charge
an arc will not jump at a greater distance than .5") I understand that the
type of material, the humidity and other factors make a difference, but
there must be some test data some where that points to some generalities.

Thanks again for your time bill

John

-----Original Message-----
From: Bill Brooks [mailto:[log in to unmask]]
Sent: Wednesday, May 04, 2005 11:03 PM
To: 'John Smith'
Subject: RE: Web site question

http://sprott.physics.wisc.edu/demobook/chapter4.htm

see table 4.2

The issue with predicting electrical arcing is in defining the environmental
conditions that contribute to the 'break over' voltage. The presence of dry
ionizing air, or ionic contamination on a surface can greatly increase the
distance at which break over will occur. Once the arc is established, it
ionizes an electrical path which is much lower in resistance that the
initial break over voltage required to jump across the electrodes and the
two points of potential can be moved much farther apart and they will still
conduct...
What are you trying to do?

Bill Brooks


-----Original Message-----
From: John Smith [mailto:[log in to unmask]]
Sent: Wednesday, May 04, 2005 2:09 PM
To: [log in to unmask]
Subject: Web site question

Is there a guideline that references how far a static charge will jump?
i.e. a 500v charge could be expected to jump or ark how far?

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