On Jan 28, 2008, at 10:56 AM, Apptech wrote:

> Cupric Chloride, fwiw.

Yeah, the etching reaction goes CuCl2 + Cu --> 2 CuCl or something  
like that, so both cupric and cuprous chloride are involved, and I  
left it as "copper chloride." :-)

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

"pirhana" is the acid/peroxide mix.  In particular, "pirahna" usually  
refers to an etchant made from CONCENTRATED sulfuric acid and  
hydrogen peroxide, widely used in the semiconductor industry cause it  
doesn't attack silicon or glass.

>
> 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.

Are you sure you're not mixing up "real" pirhana with the HCl/ 
household peroxide etchant most people use as the starting point for  
CuCl2 etchant?  IIRC, I used about half pool acid and half 3%  
peroxide for an end acid concentration of less than 20%, and didn't  
find it any worse to deal with than, say, plain HCl.  (better than  
concentrated HCl, which has obnoxious fumes.)  Of course, I did most  
of this in a "leave it running in the outbuilding for a while", and  
it didn't come close to the 10 second etch time you also mentioned...

BillW

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