Dear Wee Mei

As implied by David Douthits message, the coating has become "soft". This
may have allowed certain particulates to "adhere" to the surface - they are
not likely to "sink-in"!

These coatings are "thermo-plastic" materials, so this condition is not
surprising but, the coating is NOT becoming liquid.

If this issue cause you some reliability issues - the assembly is failing in
test or real conditions because of this condition - then you might like to
try another variant, details of which I will give you off-TechNet. It is
simply another acrylic material that has a different thermal withstand that
permits it to be less "sticky" under high temp conditions.

If you are NOT getting failures in test or service, is there a problem?

Regards, Graham Naisbitt

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www.concoat.co.uk <http://www.concoat.co.uk>

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-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of fullname
Sent: Tuesday, September 25, 2001 08:34
To: [log in to unmask]
Subject: [TN] Dirt on Coated Board (UC)


Some assembled boards were coated with Humiseal 1B31. After the ESS
tests at 110 degree C, dirts were found on the board and component
surfaces on both sides. I have checked the data specification on 1B31
and found that under cured enivronemnt, the coating should withstand -65
to +125 degree C.

Can someone advice me what could be the cause of this problems?
Your assistance is greatly appreciated.

Regards - Wee Mei

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