DI water has been used in shops for years now due the quality of the incoming water.  Chlorides and calcium deposits in incoming water makes city water to dirty to provide clean rinsing. I would advise asking your various suppliers just how clean does clean need to be. I have found that DI is an overkill based on costs. We have installed a RO unit. We have found the RO not to be as clean as DI ( about 5ppm more ) but well within acceptable limits. Suppliers will always advise you to have to best of everything as it since it is obviously less things that can affect their products. However, sometimes the best is not really warranted and results in excessive costs. Especially if your renting the DI Banks. Installing the RO unit has cut our annual DI expenses by 12k. We designed the system so we can easily place a DI Bank in line when the RO filters need to be changed and regenerated. This is the way to go!

Ed Cosper
Graphic Electronics Inc.
 
----------
From:  J. Warhelere[SMTP:[log in to unmask]]
Sent:  Saturday, February 14, 1998 4:13 PM
To:  [log in to unmask]
Subject:  [TN] Why DI?

Technet,

The recent discussion surrounding tap water versus DI for black oxide
rinses begs the question

Why use DI anywhere in the PCB shop?

Consider the processes

developers
microetches
rinses
oxide baths
oxide reduction baths
golds and nickels
immersion metals
electroless, palladium-carbon, or conductive polymer
acid cleaners
tin and tin/lead
acid copper baths
tin strip
etchers
tin/lead strip

In a past life a shop had a DI system that leached hydrochloric acid
after regeneration and maybe still does (?).  That was something in its
own to deal with.

What does one do when the DI unit needs regenerated for water?  Shut
down operations?

The input of manufacturers and users is welcomed because the issue seems
one of debate, and I'd like to hear some real facts.
Please respond by actual experience as most manufactures recommend DI,
but perhaps not all of us use DI continuously in all areas?

Or better, yet, if there are alternative water improvement systems out
there, what are they? Is there something more reliable and less cost
intense?

[log in to unmask]

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