>> When you first mix the HCL and H2O2, the etch chemistry 
>> is,
>> basicaly, free chlorine. Nasty, nasty stuff. But once 
>> you've added
>> a fair
>> bit of copper it becomes a mixture of ... > Copper 
>> chlorIDE.

Cupric Chloride, fwiw.

One name for this is "Pirhana" :-).

While the properly constituted Cupric Chloride etch bath is 
a thing of beauty and a joy forever (if properly maintained) 
and about as benign and marvellous as you could hope from an 
etchant, the prepare-from-scratch mixture is about as evil a 
substance as you would ever hope to meet. This can 'etch' a 
PCB in about 10 seconds and you'll probably never have seen 
as clean and copper free a piece of blank PCB material 
before. Once you are silly enough to get used to it you can 
etch boards credibly well in a minute or two. The fumes are 
more vicious and breathing discouraging than almost anything 
I've ever met - and I've met a fair few substances. (It's 
not certain what it is but it's probably Chlorine gas with 
vaporised acid and H2O2 mix plus probably a high Oxygen 
content as well. High lung and eye damage material and 
almost certainly carcinogenic as well.

This comes close to being a NEVER try this at home method, 
were it not for the serenely beautiful mixture that can be 
made when prepared correctly and very very very slowly and 
then used properly.

Few believe the warning signs by the way, nor heed the trail 
of gasping bleached eyed astounded forebears limping past 
from the other direction.

Here is how to do it properly and why and how it works.
Stray from the strait and narrow path and your lungs may die 
and there will be weeping and wailing and gnashing of 
(corroding) teeth and downcastness of countenance and user 
and great may be the fall thereof.


        http://www.xertech.net/Tech/CuCl_ech.html


                    Russell


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