Mail*Link(r) SMTP               FWD>Bubbles in Conformal Coating

Hi David and Dave,

David, Dave's response about residual surface contaminants is a good one, we
had some problems with inadequate cleaning of some residues under/along side
some components.  The residues reacted with the epoxy conformal coating to
form many bubbles between the component body and the surface of the printed
board.  Some of the bubbles were so numerous the bubbles were almost
"froth-like".   There were also many isolated bubbles on the surface of the
printed board -- cleaning was totally inadequate.  After we suitably "cleaned"
subsequent printed board assemblies (that were assembled using the same
process and people), all the bubble related problems went away.

Ralph Hersey
[log in to unmask]


--------------------------------------
Date: 7/29/96 9:47 AM
From: ddhillma
     Hi David:
     
     Could you be getting a turbulent flow/disruption in the Nordson 
     nozzle? What about a contaminate on the PWA that is reacting with the 
     postcoat to form bubbles?
     
     
     Dave Hillman
     Rockwell Collins
     [log in to unmask]


______________________________ Reply Separator
_________________________________
Subject: Bubbles in Conformal Coating
Author:  [log in to unmask] at ccmgw1
Date:    7/26/96 11:52 AM


     Has anyone ever experienced a problem with bubbles in conformal 
     coating when using an acrylic coating (CONAP 1171) applied with a 
     Nordson Select Coat system?  The bubbles appear instantly as the 
     coating is applied.  The result is a non-conforming defect per 
     IPC-A-610 section 7.1.2.  Thank you.
     
     
     David Bruni
     Manufacturing Engineer
     MSA
     Instrument Division
     (412) 776-8848
     
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