Hi all out there,

*Hi you in there

One of our customers is concerned with the level of flux residue (no clean)
present on RF boards - concern that the flux characteristics negatively
affects circuit perfomance (FR4 material, HASL finished is being used for
circuitry operating at 5GHz). He has thus requested to rather assemble
using
water-soluble flux. With water-soluble flux of course comes cleanliness
issues which may result in latent defects due to entrapped corrosive flux
residue. The product is spec'd to operate, uncoated at -40deg.C. Any
insights into this dilemma?

*Well, if you already have your process set up for a low solids flux, and
it is working well, don't change it.  I would only advocate going back to a
water soluble flux if you are having solderability issues or high levels of
solder defects.  If your customer is concerned about the low solids flux
residues, then remove them (the residues, not the customer).  Presumably,
you have aqueous cleaning capability if you are contemplating going to a
water soluble.  I would suggest using a suitable soap in such a cleaner,
rather than changing the flux.  Here at Rockwell, we use low solids fluxes
and pastes, but still clean them for a variety of reasons, most relating to
our control of our incoming materials.  We are working towards a true
no-clean process, but until we get adequate controls in place, we continue
to clean.  Most of our process centers use 28% Kyzen Aquanox SSA (in-line)
or Kyzen Ionox FCR (batch) with excellent results on OUR low solids flux
residues.  We also use Alpha 2110 saponifier in some locations, but that is
being phased out in favor of the Kyzen materials.  In the past, I have also
found good results with Envirogold 816, made by Envirosense.  I can get you
contacts if you like.

Overall, I would look at cleaning the residues before I would contemplate
going to an OA flux.

Doug Pauls
Rockwell Collins

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