Thanks for the reminder, Neil.

I do not remember the type of flux (it was a liquid type meant for
electronics) but I once had a circuit catch on fire (!) because of
flux I failed to clean off. The circuit was a 48V motor drive
prototype. Since it didn't contain any high-impedance circuitry and
was a quick one-off proto, I didn't think it necessary to clean off
the flux (I should note that I added flux beyond what was in the
solder to help solder to copper bus bars).

When I started it up, I saw what appeared to be arcing. It quickly
turned into a small jet of flame. I eventually figured out that the
flux was allowing a moderate resistance path from 48V to ground, and
the resulting current was heating, boiling, and igniting the flux.

Sean


On 6/12/07, PicDude <picdude2@avn-tech.com> wrote:
> I remember some brief discussion here some time back re: flux removal and some
> were saying that they don't remove flux since it has no real effect on the
> circuit.  Well, I have now proven to myself that it *does* have an effect.  I
> was tracing down some odd results at an analog PIC input and cleaning off the
> flux near the PIC's analog pins solved the problem.  BTW, this was rosin
> amine flux, and I cleaned it off a CW Rosin Flux Remover Pen.
>
> Cheers,
> -Neil.
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