Hi Kenny, Flux residue left on the board will act as a barrier between the conformal coating and intended coating surface. While newer conformal coatings have been designed to better wet soldermasks and small amounts of remaining flux residue, it is always recommended that full testing be conducted to truly understand the effect of remaining residue. The results will depend on variables including the type and amount of residue present, specific conformal coating. The flux residue barrier can lead to eventual loss of adhesion or even localized delamination of the coating in some cases. Cleaning is definitely best practice. Jon Galaska DYMAX ***************** CONFIDENTIALITY STATEMENT ********************** The information contained in this message and any attachment(s) may be privileged, confidential, proprietary or otherwise protected from disclosure and is intended solely for the use of the individual or entity to whom it is addressed. If you are not the intended recipient, you are hereby notified that any dissemination, distribution, copying or use of this message and any attachment is strictly prohibited and may be unlawful. If you have received this message in error, please notify us immediately by replying to this email and permanently delete the message from your computer. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner Sent: Thursday, March 04, 2010 1:02 PM To: [log in to unmask] Subject: Re: [TN] Conformal Coat Over No-Clean Flux Kenny, I would clean before I coat. I am no chemist but I would bet $$$ that whatever it is on the board can interfere with the coating cure/dry process. I know that no coating will stop moisture penetration and having voids or other material where water can be trapped is really bad. The amount of water within the coating is very small and the coating still remains a good insulator. But if the water meets any ionic source under the coat you have conduction at the PCB surface. If it was me I would rather go through another wash rather than coat over the flux and not understand the process. I do a little silicon spray coat on some boards. I rework with WS flux then clean. Bob Kondner -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Ken Bloomquist Sent: Thursday, March 04, 2010 12:20 PM To: [log in to unmask] Subject: [TN] Conformal Coat Over No-Clean Flux We have a twelve leaded, through-hole component that has to be hand soldered on the circuit board. The assembly gets conformal coated with urethane. We would like to hand solder these twelve leads using no-clean and then conformal coat the board. The component would be added as a final step after the assembly has first been cleaned. Since this is not a "total no-clean" process do you see any issues applying conformal coat over these twelve no-clean solder joints? Best regards, KennyB ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 -----------------------------------------------------