I would guess the "reason" for using softened water instead of DI is
that the original people who installed the system probably just looked
at the $$$ and did not appreciate that whereas DI water is soft,
softened water is not the same as DI. They were probably vaguely aware
that some water purifying systems use salt to regenerate and thought
that any system that requires salt  additions was a water purifying
system. This is completely wrong for PCB cleaning of course as you
appreciate. In your system you are adding the salt to the water itself
and therefore increasing the ionic burden not reducing it, the fact
that the water is now soft and will lather easily with soap is not all
that relevant to your needs.

So its a little difficult to suggest a rational response to an
irrational situation. I suggest you might want to proceed on the basis
that you don't have a water cleaning system at all and set out to
determine the system that you should have for your volume and quality
standards.
This should generate a machine recommendation and cleanliness
standards required, supported by outside references, then you can
compare what you've got with what you should have.....

Mike

----- Original Message -----
From: "Kathy Kuhlow" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, March 30, 2001 9:40 PM
Subject: [TN] Water Wash system justification


Help.....  I have recently been assigned the task of justifing our
water wash system.
Here is what I know:

1) Spray over Spray Westkleen system
2) For some reason using softened water not DI.  The softening is
accomplished through sodium addidtives (got me going).

What I am expected to do:  Determine what is the effectiveness of the
process.  Justify why DI isn't used and why adding salt to the wash to
remove salt is ok.  Then determine the water surface tension and
content (hardness, contaminates present, etc)

TIA
KK

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