Charlie

This kind of flux is not, strictly speaking, OA. However, ALL fluxes
used in electronics are both organic and acid, so this designation is
meaningless, anyway. What you refer to is what is better described as
water-soluble. The flux Neil is using is not necessarily water-soluble,
i.e. the residues may or may not be soluble in water, but the flux
itself uses water largely as its solvent. The secret of this kind of
flux is to apply a precisely metered quantity of solids per unit area of
board, sufficient to do the job, without an excess. There will then be
just the metal salts and a really minimal quantity of flux left on the
board at the end, the rest having sublimated in the wave. If you apply
too much, then you are in Trouble, with a capital T. It is a tight rope
act applying sufficient to do the job but not enough to cause trouble
later.

I agree that for high humidity service conditions, Neil would possibly
be better off using a water-soluble flux and washing or, if he must go
the "no-clean" path, using a very lightly activated rosin or a synthetic
resin flux. With the water-soluble path, he will have a very wide and
tolerant operating window: with "no-clean", under these circumstances,
it will be very narrow, with no room for errors.

Brian

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