Jean-Francois

As you will have seen, Brian gives you the full technical low-down but, to
perhaps simplify the situation think of it this way:

To my knowledge, Conformal Coating Materials are not intelligent. They stick
or adhere to you components, component legs, bare track or solder joints but
not to the solder resist or perhaps flux residues (do you know which?) - so
how do the coatings know the difference?

Of course they don't. Clearly something is influencing the adhesion. Is this
a problem. Do your assemblies fail in test or are you just unhappy with the
adhesion? If they pass your tests but the coating doesn't stick too good, do
you really have a problem? Only you can answer these.

The issue is perhaps a little broader in that manufacturers of solder
resists, solder fluxes use surfactant additives to aid wetting and
levelling. For example, how do they get a liquid with only 2% solids or less
to remain on the surface whilst inverted? (Viz no clean spray or foamed
flux) The problem is that these surfactants may well react in an
unpredictable way with all your other process chemistries which exhibits an
adhesion problem for the coating.

As Brian rightly said, it is unlikely that the vendors know unless they have
tested materials themselves or produce them, themselves. Hope this helps -
BTW there is more about this on my web site www.concoat.co.uk for anyone who
cares to look
Regards
Graham Naisbitt
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Web: www.concoat.co.uk
Concoat Ltd
Alasan House, Albany Park
CAMBERLEY GU16 7PH
Tel: +44 (0) 1276 691100
Fax: +44 (0) 1276 691227

  -----Original Message-----
  From: TechNet [mailto:[log in to unmask]]On Behalf Of Bissonnette,
Jean-Francois
  Sent: Thursday, November 09, 2000 07:34
  To: [log in to unmask]
  Subject: [TN] Conformal coating and no clean flux.


  Did anyone have any kind of problem with coating adhesion when using
  "no clean" flux (manual repair and reworks)?  I've been told that by some
  tech here and I have no time to experiment with it.

  And is "no clean" flux really "NO CLEAN" anyway???

  JF


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