Regarding Mr. Fritz's point about cascading water back
into the rinse chamber:

<<<I don't think the cascade rinse section can be
successfully run with water. Years ago, some etchers
were made with fog nozzle type rinses (very
low water flow) so that the very small volume of water
could be sent back to the alkaline etch supplier.
This was an attempt at "zero discharge to
the drain" etching. Water should NEVER be cascaded
back into the sump as that will disrupt the chloride
balance in the etchant and sludge out the etcher.>>>>

Stated another way: water cascaded back into the
etcher will dilute the contents of the sump, and
reduce the chloride concentration on a volume basis.
This is actually desireable from the standpoint of
reducing undercut, so long as you don't go too low and
sludge out.  Naturally, it depends on the amount of
water you use, which depends on the number of rinse
stages you use and the dragout rate from your etch
chamber.

Peter Blokhuis

--- Naftali Farchi <[log in to unmask]> wrote:
>
*************************************************************************
> NAFTALI FARCHI CHIEF PROCESS ENGINEER
> TEL: 972-3-9395031
> FAX:972-3-9309581
> mailto:[log in to unmask]
>
> > -----Original Message-----
> > From: Dennis Fritz [SMTP:[log in to unmask]]
> > Sent: á îøõ 19 2001 5:35
> > To:   [log in to unmask]
> > Subject:      Re: [TN] Dry Film Breakdown In
> Ammoiacal Etching
> >
> > Larry,
> >
> > Yes, you are on the right track to controlling dry
> film breakdown in the
> > ammoniacal etcher.  Be sure to split the feed
> between the cascade rinse
> > and
> > direct to the main sump.  That will keep the pH in
> the cascade rinse down
> > (your problem with the dry film).
> >
> > I don't think the cascade rinse section can be
> successfully run with
> > water.
> > Years ago, some etchers were made with fog nozzle
> type rinses (very low
> > water
> > flow) so that the very small volume of water could
> be sent back to the
> > alkaline etch supplier.  This was an attempt at
> "zero discharge to the
> > drain"
> > etching. Water should NEVER be cascaded back into
> the sump as that will
> > disrupt the chloride balance in the etchant and
> sludge out the etcher.
> >
> > You may have to consider a dry film with more pH
> tolerance in this
> > application to allow you to occasionally make 2
> ounce layers or even
> > heavier
> > copper cores as required.
> >
> > Let us know off line if further direct help is
> required.
> >
> > Dennis Fritz
> > MacDermid, Inc
> >
> >
>
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