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June 2000

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Subject:
From:
Kiiski Jarmo <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 19 Jun 2000 09:54:41 +0300
Content-Type:
text/plain
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We in middle of Finland have used artificial ground water for washing PCA's
after wave soldering with water-soluble flux for over ten years with
excellent results. The quality of water is:
pH: 8,5
Hardness: 2 dH (soft)
Conductivity: 100 microS.

Don't understand that so that if you have similar water, you will get
similar excellent results. It only shows that it is possible.

The quality of water is one of the most important factors when washing PCA's
among the time and temperature. I believe that this conversation has been
very useful for many of us. Sometimes very simple thing (like just water)
can turn very complex matter and things are not any more like they were
before. I appreciate courage and enthusiasm of you all TechNetters to share
you knowledge with this community.

B.R.
Jarmo Kiiski

> -----Original Message-----
> From: Brian Ellis [SMTP:[log in to unmask]]
> Sent: 17. kesäkuuta 2000 11:12
> To:   [log in to unmask]
> Subject:      Re: [TN] Chloride - Chlorine
>
> Sorry, Franklin, it is not semantics. You are putting forward a scientific
> statement
> and the essence of science is precision. Hopefully, your "crystalline
> growths" were
> mostly calcium/magnesium hydroxides, carbonates and hydrocarbonates, which
> are common
> in many tap waters, rather than chlorides. Calcium chloride is
> physiologically not very
> good, especially for children, and excess sodium chloride (>~400 mg/l) is
> worse for
> hypertensive patients.
>
> Interestingly, chlorination can produce minute amounts of hydrochloric
> acid if the
> water has a heavy microorganic content and this may react with dissolved
> calcium
> hydroxide (lime) to produce calcium chloride, but the quantities involved
> are
> negligible. Care should always be taken to introduce sufficient chlorine
> to kill off
> the microorganisms but not sufficient excess chlorine that the water
> becomes
> objectionably odoriferous. It is for this reason that UV irradiation is
> sometimes
> preferred, by itself or as a pretreatment before a milder chlorination, as
> a biocide,
> e.g. in desalination plants for potable water. Incidentally, the NaCl
> limit for many
> desalination plants is ~400 - 800 mg/l, but this is often mixed with
> ground water or
> other sources in the reservoirs, to dilute it down to under 200 - 300 mg/l
> NaCl. About
> 800 mg/l is the threshold of taste.
>
> Anyway, not all municipal water is bad. In Scotland, for instance, many
> highland lochs
> have negligible TDS. In fact, Loch Katrine is a major reservoir for
> Glasgow and they
> actually add some lime to it because the water is so soft, with a pH of
> about 5,5, that
> it corrodes the cast iron conduits (not to mention kid's teeth and bones).
> In Glasgow,
> before the 39-45 war, over 1/3 of the kids had rickets in some degree or
> other because
> the water was so poor in calcium and they drank little milk (heavily
> depressed area and
> milk was beyond the purses of many households). I know some plants in some
> parts of
> Scotland that use unpurified water for  cleaning PCBs, quite successfully,
> but this is
> the exception that proves your generalisation.
>
> Brian
>
> Franklin D Asbell wrote:
>
> > Semantics, or the wrong choice of word, contaminates in the city water
> > rinse used at that company caused crystalline growth as evident by SEM
> > and Auger analysis.
> >
> > The point being city water....bad!!!
> >
> > ~grin~
> >
> > Sorry to stir the pot...
> >
> > Franklin
> >
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