I wonder why there is so much mystery in etch
solutions, like "A special Metal A etch solution" with
"proprietary composition made by company XY" etc. Ti
etch solutions are known for ages, EDTA is one,
mixture of NH4OH/H2O2 is another one. The later one
with the ratio 1:3 etches 100 nm of Ti in about a
minute or a bit faster.
Al etch solution was always Phosphoric Acid (H3PO4)
with a bit of Acetic Acid, water a surfactant, which
does not contain sodium (triton).
I would suggest all folks here before they strat to
believe in a mysterious proprietary compositions  of
anything to check a book: A Handbook of Metal Etchants
by CRC press. The other option is to check MSDS data
sheets as the complete composition is shown there.
Pavel Neuzil
Advanced Infrared Pte Ltd

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