I agree that you don't want the residue from hard water left on anything, but in reality, most of the rinse water will (should) be removed by air-blasting. There can be some left for evaporation, but the main thing is to somehow get most liquid water out of there right after rinsing.
Water is actually a very potent solvent, so going to extremes to "purify" it are futile. If you dump a bucket of DI water on a board it will just strip some of the metal ions from the materials in order to re-ionize, and can still leave stuff behind when it evaporates. In a high purity environment like washing processed silicon, there isn't much stuff to react with except the targeted contaminants, but in a practical environment, it won't remain DI for very long.
I have washed many boards in tap water with liquid detergents (non-ionic surfactants), then thoroughly tap water rinsed, then thoroughly shaken out or air blasted, and finally oven-dried.
Scaled up to a whole scope, the process would include rinsing with a garden hose, then air blasting, then sun-drying for a few days, maybe with a fan blowing at it.
Ed
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--- In TekScopes@..., "Rob" <rgwood@...> wrote:
It is a bit more complicated than just the ions and what is left after
evaporation/boiling on soft water vs. hard, etc. I don't want to get to
technical nor argumentative. However soft water via ion exchange is better
than hard water (because it rinses better). However it is not as good as RO
or distilled, etc.
So yes soft water does imply conductivity as the ions are simply swapped for
different. Soft does however leave less gunk around after washing and
rinsing than a hard water alternative (solubility of the ions is the
driver... calcium in particular has a negative solubility) even though it is
simply different ions as others have already said/pointed out.
Bottom line I would not use hard water, I would consider soft water in a
pinch but would prefer RO or distilled. I assume after all that soaps of
some kind are involved so rinsing ability is likely key.
All that said, I have refrained from using water as I do not have good
drying methods at my disposal. In addition, it still just seams "wrong"
somehow to me to mix water and electronics (especially socketed, etc.)...
Rob
-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...] On Behalf
Of John Griessen
Sent: Wednesday, July 11, 2012 6:04 PM
To: TekScopes@...
Subject: Re: [TekScopes] Notes about washing Tektronix Oscillosopes
On 07/11/2012 04:58 PM, David wrote:
Softened
water was an improvement for washing PC boards but we still rinsed in
distilled water or water from reverse osmosis.
Ah, so...
ion exchange (water softener system) does imply conductive/salty as I was
thinking.
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