With a former employer I saw boards assembled at a shop with a water soluble
flux, then sent to us for test and installation. Typical cycle time was less
than two weeks. They used a little batch cleaner. We did get boards
exhibiting green copper.

The flux container cautioned users that cleaning should be initiated before
the boards cooled and stated that "greening" could occur within 24 hours.
Since they were a wholly owned subsidiary, I forced them to a less
aggressive flux, still water soluble. We never saw the problem again.

> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Kane, Joseph E
> Sent: Wednesday, May 26, 2004 10:47 AM
> To: [log in to unmask]
> Subject: [TN] WSF Corrosion In A Shop Environment
>
> We're talking with our customers about converting from RMA to
> an ORH1 water soluble flux for wave soldering.  We've
> completed qualification testing per J-STD-001, but they have
> some questions.
>
> We'll be cleaning with an in-line system right after wave.
> Before conformal coat, we plan to clean 100% in a batch
> system with 75% isopropanol and DI water.  Sump resistivity
> is monitored, so we will be performing 100% ROSE test on each lot.
>
> Customer wonders what happens if there is any WSF residue at
> all left on the boards between the time they are cleaned with
> the in-line and the final cleaning stage.  Allowing time for
> hand soldering and Genrad test, this is usually a day or two,
> but in the extreme, it could be weeks.
>
> They have the impression that WSF residues are strongly
> corrosive, and the boards could turn to mush.  We have a
> board that was soldered in November and hasn't been cleaned,
> and solder joints are still shiny.
>
> Question is this - any known instances of corrosion happening
> in an air-conditioned shop?
>
> Joe Kane
> BAE SYSTEMS Controls
> Johnson City, NY

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