There have been many helpful comments on this already, so at the risk of
being redundant here are just a couple more:

Probably the most commonly used micro-etch for copper is ammonia /
peroxide which is easy to get, simple to make up (but it must be freshly
made each time) and is fairly harmless to work with.

Metallography on thin copper is a bit of an art. Labs that do it all the
time know the pitfalls, but heed Werner's warning against using just any
lab. The apparent grain structure can be changed significantly by the
act of preparing the sample itself.

While classic copper annealing is done at relatively high temperatures
(600F), it's possible to anneal wrought copper foil at temperatures as
low as 325F in a couple of hours. (The difference being made up by the
residual energy stored in the grains during the rolling process.) This
depression of the annealing time & temperature is typically designed in
by the foil manufacturer to suit the needs of the printed circuit
industry and matches well with common lamination cycles. In most cases
recrystallization only occurs at temperatures above 700F.

Andy Magee
Flex Guru - Consulting
[log in to unmask]
(937) 435-3629

ps. Yes, among other things I have an MS in Metallurgy.

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