Dear Mike:

One of our customers was confronted with this problem within the last two years.  The
accumulation of this residue was a concern due to its potential as a contributing
factor in superfluous copper.  We collected a sample of the residue and tested the
material via FTIR, comparing the scan to FTIR fingerprints of the etch resist and
elastomers used in guides and pinch rollers within the conveyor.  It was our opinion
the residue probably contained elements of both the photopolymer and elastomer, due to
breakdown caused by the cupric etchant.

It was also believed the rate of black residue accumulation increased as the
hydrochloric acid normality of the etchant increased.  The installation of carbon
filtration was beneficial.  You may want to cosider trialing carbon filtration as well
as reducing the acid normality.

Regards,
Ted Stern

Mike Bailey wrote:

> We recently installed a new DES line using cupric chloride with sodium
> chlorate regeneration.  We have been experiencing a blue/black residue that
> coats the etch filters and seems to find it's way into the spray nozzles
> etc. etc.  We beat the fluoride theory and seal degradation to death and
> have found nothing substantial.  I have been told that others have
> experienced this problem and have attributed it to various causes such as
> developer drag-in, anti-foam contamination and leaching of dryfilm organics.
> I've also heard of others that have retrofitted carbon filtering systems on
> to their etchant recirculation pumps. I should note that this is brand new
> "high end" equipment with plenty of water rinse stations and blow-off
> modules.  Does anyone have any experiences they would care to share? Thanks
> in advance.
>
> Mike Bailey
> Director of Engineering
> McCurdy Circuits Inc.
> 4900 E. Hunter Ave.
> Anaheim, CA  92870
> Phone: 714 507-4900 Ext 253
> FAX: 714 507-4911
> e-mail: [log in to unmask] <mailto:[log in to unmask]>
>
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