Doug,

I had that same thought when I saw the process down in Clearwater, but soon
reconciled to myself that I was being overly cautious.  As you mentioned,
the feed lines are at least static dissipative and the nozzle is conductive
(and tied to ground).  I would have greater fears if the nozzle were
composed totally of ceramics, but then as Brian pointed out, the 'flame'
(arc) is essentially a plasma - which should be a mix of positve and
negative ions.  I worried more about the possibility of partially molten
'large' agglomerates causing physical damage upon impact.

Also consider the total composition of what is being deposited!

Steven Creswick
Gentex Corporation

-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Friday, July 06, 2001 12:50 PM
To: [log in to unmask]
Subject: [TN] ESD of molten ceramic


good day all,

Here is one from extreme left field:  we coat one of our chips with a
thermal spray process involving what is essentially a stream of molten
ceramic material.  The ceramic powder flows through a static dissipative
tube and goes out the metal torch, where the flame heats it to molten state
as it sprays.  The molten spray is deposited on the chip package surface,
which are mounted in a spinning aluminum wheel, which is grounded.  Here is
the question:

Have any of you seen (or have) data that suggests that molten ceramic
particles, flying through nitrogen-enriched air, generate static
electricity, keeping in mind that the supply tube, the torch and the target
are all grounded?

Doug Pauls
Rockwell

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