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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