One obstacle to be able to "hold a narrow etch rate window with fewer bath
changes" that has not been mentioned as yet is the fact that commercial
copper foils do not have fixed etch rates. Just as other properties of Cu
foils, like strength, ductility, specific gravity, electrical conductivity
can vary even from lot to lot from the same foil manufacturer, so does etch
rate. This variability comes from variations in the plating chemistries,
which as I understand causes a variation in the amount of bath constituents,
such as organics, to be plated out at the grain boundaries. The more such
materials are co-deposited at the grain boundaries, the lower the previously
mentioned properties except etch rate, which goes up.  

Werner Engelmaier
Engelmaier Associates, Inc.
Electronic Packaging, Interconnection and Reliability Consulting
23 Gunther Street
Mendham, NJ  07945  USA
Phone & Fax: 201-543-2747
E-mail: [log in to unmask]


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