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Inge:
There are ESD safe brushes that are impregnated with Carbon.
Also if the process is done in a chamber that is humidified by a
current of moist air and the air goes over ionization bars the problem
is diminished considerably. You may also consider a short rinse with
ionized water, blow them dry with ionized air and then a bake. Even
though you state that it is not allowed, from experience, it works well.
Regards,
Ramon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar
Sent: Tuesday, March 27, 2007 7:09 AM
To: [log in to unmask]
Subject: [TN] ESD charges in conformal coatings
Hi all gnus and gurus,
Sometimes, we need clean boards from dust and dirt. Field practise, no
proffesional facilities. Not surprisingly, you move electrons from the
conformal coating's surface. I have measured several kilovolts at a
distance of one inch from the board. The highly insulating acrylic
coating keeps the charges effectively for hours, quite expected too. ESD
brushes not much better. Not even grounded ESD brushes works. I get rid
of the surface charges if I dip the board in water, quite natural,
because of the large contact area and polarisation media. EE in the US,
did an investigation during 8 years. They ranged the 23 most common
electrical failures and their sources. Conformal coating charges came as
number 9.
Question: anyone who can recommend a dust and dirt removal method, when
dry brushes don't work and water is not allowed?
Inge
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