Consider condensed moisture getting into the material during the spray process, being trapped and later vaporizing during the cure process (or even after?). When we get bubbles it is usually because of a too heavy first coat or not allowing solvent vapors to escape before the material gets too hard to allow vapor escape (without making bubbles). Perform a drying bake-out before coating. Allow a short time between coats for vapor evaporation, cure at a lower temp to allow water vapor to escape before material gets too viscous. > Rainer G. Blomberg > Honeywell -Space Systems Clearwater > Staff Production Engineer (727) 539-5534 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Kelly Morris Sent: Tuesday, January 24, 2006 10:25 AM To: [log in to unmask] Subject: [TN] Conforma Coat (Urethane) & bubbles We've got a problem here, where we're hand spraying a urethane conformal coat on over a rectangular inductor. The inductor body is a plastic tube, with potting to fill. The top is not always flat (sometimes concave). The problem is that bubbles appear in the conformal coat on the potted surface, sometimes right after bake and sometimes days after. Any ideas on what the root cause is and how to prevent the bubbles? --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------