The following are some tips on running alkaline etchant, especially where
production volume has decreased.

1. Alkaline etchants are formulated with ammonia and chloride contents
appropriate for percentage operating time.  You may have now "hitched a race
horse to an ox cart" so to speak.  You may want to contact your vendor to
change to a product more suited to your present operation, just as when your
volume went up, you traded your ox for the race horse.

Why is that?  Race horse etchants are formulated for say 75% operation time
and frequent sump turnover, -  with high chloride (copper capacity) and lower
excess ammonia (little idle time for ammonia evaporation).

2. As much as possible, group your etching work into "bursts" of activity.
Close down the dampers and shut off the sump heat when the etcher is not in
use.

3. Decrease the sump volume as much as possible with glass bricks, or similar
inert media.  This will allow more sump turnovers of the spent etchant per
week.  Calculate the turnover time for your sump - If it is longer than a
couple of days - you are going to be fighting add-backs of anhydrous ammonia,
or walking a tightrope with aqua ammonia  add-backs.

Rudy misses one point in specificaions on incoming alkaline etchant.
Essentially all alkaline etchant uses recycle ammonia, and rest assured the
copper in spent etchant is reclaimed.  This  ammonia recycle step means the
spec is wider than for formulated products, but when you need to brag about
recycle in your shop, point out that BOTH the copper and the ammonia in your
spent alkaline etch get recycled.

Denny Fritz
MacDermid, Inc.

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