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> -----Original Message-----
> From: Dennis Fritz [SMTP:[log in to unmask]]
> Sent: ב מרץ 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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