When I think of soft water I think of drinking water and household water
softeners. We soften household water to reduce the formation of scale
around faucets and drains and to improve performance of soap.

I have water softeners used in factories for in-line cleaners. I think
it is a bad idea. Here is the line on water softeners, just a few
minutes with our old friend Google.

http://www.csicop.org/si/9801/powell.html
Water "hardness" is a measure of dissolved mineral content. Water
hardness is quantified by the concentration of dissolved hardness
minerals. The most common hardness minerals are carbonates and sulfates
of magnesium and calcium. Water with a total hardness mineral
concentration of less than about 17 parts per million (ppm) is
categorized as "soft" by the Water Quality Association (Harrison 1993).
"Moderately hard" water has a concentration of 60 to 120 ppm. "Very
hard" water exceeds 180 ppm.

http://www.sciam.com/askexpert_question.cfm?articleID=0003401A-597A-1C72
-9EB7809EC588F2D7
Most water softeners remove problematic dissolved magnesium and calcium
by passing water through a bed of "ion-exchange" beads. The beads are
initially contacted with a concentrated salt (sodium chloride) solution
to saturate the bead exchange sites with sodium ions. These ion-exchange
sites have a greater affinity for calcium and magnesium, so when hard
water is passed through the beads the calcium and magnesium ions are
captured and sodium is released. The end result is that the calcium and
magnesium ions in the hard water are replaced by sodium ions. The
process adds about 750 milligrams of sodium to each gallon of water.

Water Softeners may have a place in a good water treatment system before
a reverse osmosis process. Sodium is easier to purge from the RO
membranes than is calcium and magnesium.

But, "softened" water, if allowed to dry on a PWB, will leave sodium on
the board. I think that is a bad thing.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Macko, Joe
@ IEC
Sent: Tuesday, August 19, 2003 7:02 PM
To: [log in to unmask]
Subject: [TN] water soluble flux in line cleaner water wash


Fellow Techies,
Hopefully, someone can shed some light on my concern about rinsing
boards (soldered with water soluble flux) with softened water vs. DI
water.
A board assembly house suggested that it is acceptable to do in-process
rinsing using "softened" water (in an in-line cleaner) and save the "DI
water" rinse for the FINAL in-line cleaning.  In-process cleaning would
be for example after the 1st side is soldered on a double sided board.
Seems like a lot of extra work to me switching from softened to DI
water.
Look forward to your comments.
thanks
joe

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