Jack, Not knowing your CC, nor your potting compound, I would say this - The potting compound may adhere to the CC, but I bet the CC won't adhere to the board nearly as well as the potting would adhere to the bare board. CC/PWB interface sounds like a weak interface to me - well, so does the CC/potting ... On the other hand, the potting compound may not adhere well to the CC. Not knowing the form of your assembly, this could also present some real problems. I would most likely pot first, then CC [In my mind I picture a high modulus epoxy-based potting compound and a much much lower modulus CC. Does not sound like a happy party]. Steve Creswick http://www.linkedin.com/in/stevencreswick 616 834 1883 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Jack Olson Sent: Wednesday, June 29, 2011 12:16 PM To: [log in to unmask] Subject: Re: [TN] Potting over Conformal Coat? profound thoughts, sensei... (thanks) Another colleague here speculated that the type of potting compound being used was so "hard" that the conformal coat provided a buffer zone for thermal cycling. That was a new concept to me, this is an older product. onward thru the fog, Jack . On Wed, Jun 29, 2011 at 10:59 AM, <[log in to unmask]> wrote: > > Jack you ask a very broad question. I shall use my stock answer of "It > Depends". > > Conformal coating can be applied prior to conformal coating, but you have > to ask why. Usually your potting material provides your environmental > protection. Conformal coating is then non-value added. If it is there to > protect your assembly from the potting material, you probably have the wrong > potting material chosen. > > Are there constituents in potting compounds that can affect components? > Sure. There are lots of compounds out there. Choose wisely. > > Are there residues that can inhibit potting cure? Absolutely. Clean > carefully. Test thoroughly. Choose wisely. > > I feel like the Knight in Indiana Jones and the Last Crusade.... > > Doug Pauls > > > *Jack Olson <[log in to unmask]>* > Sent by: TechNet <[log in to unmask]> > > 06/29/2011 10:39 AM > Please respond to > TechNet E-Mail Forum <[log in to unmask]>; Please respond to > Jack Olson <[log in to unmask]> > > To > <[log in to unmask]> > cc > Subject > [TN] Potting over Conformal Coat? > > > > > Are any of you familiar with conformal coating assemblies before applying > potting compound? > > Are there potting compounds that contain harsh chemicals that could affect > components? > or > Are there residues on boards that can affect the curing properties of > potting compounds? > > I can only find one vague sentence about this in the Working Draft of > IPC-HDBK-850 > (3.12.9.1 Compatibility) > > thanks, > Jack > > > > ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 16.0 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 For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 16.0 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 For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------