If WS609 is what I think it is, the best answer is 30 minutes max. I
believe this flux is an amine-hydrochloride activated product and the
residues may contain hydrochloric acid which is highly ionic and
corrosive. I think it will also contain some surfactant which, almost by
definition, is hygroscopic. You therefore have all the makings of a
catastrophe in an uncleaned state. The ideal would be to start the wash
process when it had cooled to the same temperature as your prewash,
about 50°C.
In days of old, when knights were bold, and SMT wasn't invented,
MIL-P-28809 recommended cleaning should start within 1 hour of soldering
and that was with approved non-corrosive RMA fluxes to MIL-F-13949 (I
think). The UK DEF-Spec, which allowed the use of WS fluxes for military
applications, it was stated to the effect that cleaning should start as
soon as possible after soldering.
Brian
Linda Langley wrote:
>
> Can anyone tell me or direct me to documentation that specify how long flux residue from WS609 63/37 can be left on a board before washing?
>
> I was informed that it could be left on for 7 days .
>
> Linda Langley
> Jabil Circuit
> Training Specialist
> (248) 292-6176
>
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