Dear Chuck:

First, I would recommend reviewing a the two part (maybe three part?) article written
by Dr. Karl Dietz in Circuitree.  I think it appeared in the Nov, Dec, and/or Jan
1999-2000 issues.

Second, in our experience stripping from double treated foil has not been any more
problematic than stripping from standard foil or DSTF copper.  But keep in mind the
mechanical parameters (and/or limitations) of dry-film stripping are at least as
important as the chemical parameters, especially with double treat.  Optimizing the
spray pattern, the pressure with respect to manifold pump limitations, and the
temperature are critical.

You should be asking vendors to recommend formulations specific to the dry film you are
employing, in order to obtain optimum speed and resist particulate of suitable size for
filtering.  Effecient filtering of resist particulate can reduce chemical use by 25 -
50%, saving you money on the front and back end (volume of spent requiring waste
treatment).  Additionally, good filtration will reduce the liklihood for particulate
redeposition that can contribute to excess copper and/or potential shorts.  (Keep in
mind the use of antifoam, both type and volume employed, can contribute signifcantly to
the potential for particulate redeposition by coagulating with dry film particulate and
adhering to guide rollers.)

Regarding waste treatment, a good dry film stripper formulation should keep copper
attack to a minimum (less than 10 mg/L, perhaps even 5 mg/L) in the spent stripper.  If
you operate on a feed/bleed basis (recommended), you will have the bleed and spent bath
which must be treated.  Aside from copper, spent stripper generally exhibitis 40,000 -
80,000 mg/L COD (chemical oxygen demand).  In a feed/bleed mode, roughly five (5)
gallons of bleed should be generated for every 1,500 - 18 x 24 panels processed.  There
are numerous methods to treat spent baths exclusive carbamates.  As this is a lengthy
discussion, feel free to contact me or any of the numerous vendors supplying waste
treat chemistries/processes.

Good Luck Chuck,

Ted Stern

Chuck Brummer wrote:

> We are about to evaluate new resist stripping chemistries.  I know I
> will need one of the ME based strippers.  I was hoping those of you who
> use Double Treated copper could share your experience.  I need a
> chemical that will strip the dry film (aqueous) from the double treat
> copper, leave the copper very clean and stains to a minimum and I want
> to be able to treat the spent chemical without endangering my
> operators.  I understand that in the new future we will not be able to
> precipitate copper using the carbamate based chemicals and worry when
> operators are cleaning the filter cake.
>
> Thanks in advance
>
> Chuck Brummer
> [log in to unmask]
> 818.734.4930
>
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