I have similar experience along with Jon on this topic. Intuitively, one
would think that the residues would hamper good adhesion of the coating
to the substrate, but that's not the case if the flux residue film level
is rather low.  The uncured/wet coating will actually dissolve some of
this residue and disperse them into the coating itself, thereby somewhat
cleaning the substrate surface. For adhesive reasons, it's better to
have the residue in the coating body rather than the coating to
substrate interface. Two points of caution:

*Firstly, the flux residues can still become conductive beneath the
coating.  The same design concerns as for uncoated PWA's are warranted.

* Secondly, some coatings with Palladium catalysts can be effected by
certain organic acids found in some flux residues. This could result in
uncured soft spots of coating, above these areas of flux residue
concentrations. 

 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of [log in to unmask]
Sent: Wednesday, January 28, 2004 8:49 PM
To: [log in to unmask]
Subject: Re: [TN] conformal coat over no clean flux residue


We coated literally millions of airbag control modules per year for
several years with Acrylic, and they always passed every kind of
qualification testing.  That is a no clean soldering process under AR
coating with a safety critical application in very high volume.

By His grace,
Jon

Stop telling God how big your storm is. Instead tell your storm how big
your GOD is.

---------------------------------------------------
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
847-509-9700 ext.5315
-----------------------------------------------------

---------------------------------------------------
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 847-509-9700 ext.5315
-----------------------------------------------------