I had to do this a few years ago, same coat used both Humiseal and another brand the name of which has escaped memory. Both worked well enough for small areas but when we had to strip entire boards it was a mess. The coat turns to a gel that is difficult to remove from tight areas, like around IC leads. Be warned that some part markings and even the silkscreen on the PWB may be lost. I had to have my best artist hand letter all of the reference designators back on two boards. And she was not happy.
Charles Caswell
Process Lead, PCB
Frontier Electronic Systems
-----Original Message-----
From: Bogert [mailto:[log in to unmask]]
Sent: Tuesday, October 02, 2001 4:25 PM
To: [log in to unmask]
Subject: [TN] Seeking Conformal Coating (Type UR) Removal Process by Solvent Dipping

10/2/2001
 
Folks, I am seeking technical help on the pros/cons of removing Humiseal Type 1A33 conformal coating (MIL Spec Type UR) using Humiseal 1063 Stripper Solvent, or any other solvent that can remove the coating by dipping.  We are returning boards from the field for a significant amount of rework where removal of coating by conventional means such as by soldering iron or spot application of solvents is not practical.  The boards are FR4 base material (0.063 to 0.125 inch thick) with all parts being plated-thru-hole military specification parts.  There are parts such as connectors and numerous Integrated Circuit sockets where the stripper material could get into. There are also a significant number of teflon insulated stranded wire jumpers that are fastened to the board using RTV covered over with conformal coating. The OEM plans on dipping the complete board in a pan of Humiseal 1063 liquid and leaving it sit till the coating is dissolved.  Cleaning will then be done using alcohol with DI water applied manually followed by automatic cleaning via in-line cleaner using solvent and DI water.  Omega Meter type ionic test will then be done on sample basis to verify the ionic contamination has been removed (Humiseal 1063 stripper is highly conductive).
 
Has anyone out there removed conformal coating using Humiseal 1063 stripper or other solvent dipping process.  If so, please advise if you found the process technically acceptable, and please provide specific process details, including the post cleaning method used.  I would appreciate an answer as soon as possible.Thanks.
 
I can be reached at following contact:
 
Les Bogert
Bechtel Plant Machinery Inc.
412-829-8489
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FAX 412-825-8997