At the assembly level, we have found bare board cleanliness to be one
of the major factors in our product reliability, particularly as we move
more products into no-clean chemistries / processes.  The only way we
have seen incoming product reach our requirements of <2 ug/sq in NaCl
equivalence is when the final cleaning process at the PCB shop is a
heated (120 - 140 F) DI water process.  This is increasingly true for
HASL finishes.

Jon Moore
TRW

>>> "J. Warhelere" <[log in to unmask]> 02/14/98 04:12pm >>>
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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