What we found was the coating being used in our spray booth and
automated system was using a different carrier agent then what came in
the can. When the board house was testing boards, for their ability to
accept conformal coating, they used the can material and had better
results. I actually took one unpopulated array and sprayed half of it
with the material from a can and the other half with the material we
were using in our process. There was a distinct difference between the
two. If memory serves me right the process material was cut with toluene
and the material in the can was cut with MEK. I don't work there any
more but I am sure I can send one of the QE's an email and get some
photos. 

Ted T.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Graham Naisbitt
Sent: Monday, August 24, 2009 5:58 AM
To: [log in to unmask]
Subject: Re: [TN] Manual spraying

Ah ha!

So it would seem that the coating is soaking into the board surface  
which might suggest a resist starvation?

If you can, try a brush coat from "pure" material and see if the same  
condition recurs.

Aerosols generally speaking have ***all solids in them often less than  
5% - and its an expensive packaging medium - which is why I always  
recommend hand spraying if spraying is your preferred/required  
application method (dipping is bestest!) - Hand spray should allow you  
to get up around 20%+ solids from dipping which is at full strength  
~35-40% (1B31). Consequently aerosols might exhibit "poor coating"  
finishes more readily - because there's ***all there to begin with.

Let me know

Regards

Graham Naisbitt

Email: [log in to unmask]
Phone: +44 (0)12 5252 1500
Web: www.gen3systems.com

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