The best etchant we've found is the standard Ammonium hydroxide/water/peroxide
mixture. I would be concerned that you don't ALWAYS see demarcations due to
the board being pulled from the tank. You should be able to see not only the
grain structure but clearly see multiple plating strikes, and of course a
sharp interface between the plated copper, electroless copper and copper foil.
If you're not seeing all this, you can easily miss defects such as post
separation and foil cracking. 

Here are some tips on using the Etchant. Note that different types of copper 
chemistries may etch a bit differently. If you are only working with your own 
boards, this shouldn't be a problem. 

1)The ammonium hydroxide should be 28% reagent grade.
2)distilled or DI water is not necessary. Filtered water works best for us.
3)use 3% hydrogen peroxide 
4)make sure the peroxide comes in a dark bottle, and keep it in a dark, cold 
location. We actually go to the local pharmacy and buy it there. It comes in a 
dark brown bottle (light degrades it) and we keep it in the refrigerator. 
5)Mix the NH4OH/DI water/Peroxide in a 5:5:2 ratio
6)gently swab the microsection using a cotton ball that has been soaked in the 
etchant for 2 to 6 seconds (depending on the copper)
7)rinse the sample immediately with tap water and clean with alcohol before 
drying.  

We have a premixed bottle filled with 50% NH4OH and  50% Water. When its 
time to etch samples, we mix 10 parts of this mixture with 2 parts of the 3% 
hydrogen peroxide. Its important to mix the etchant fresh each time you need 
it for consistency.  We went to this method due to problems you mention below. 
IF you have any questions, call me.

Regards,
Paul Terranova
DIGITAL Analytical and Environmental Test Services Lab
508-467-3109
[log in to unmask]

===========================================================================
Technetters,
I am searching for the best way to etch a microsection. The way we
currently do it is Hydrogen peroxide/ammonia. It seems inconsistent as
it is used throughout the day. When the etch is new we get an extremely
good line of demarcation between the clad and plated copper.
Occasionally, we see  a line where the plater actually pulls the rack
out of the bath,  plugs the hole and returns it to the bath for a higher
thickness. We apply the etch with a cotton swab for approximately 10
seconds.

I am  wondering if this is a common technique  for microsection etching? 

T.A. Gaylor 

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