Homebrew PCBs

On 11/11/10 01:31, DJ Delorie wrote:
> The usual recipies are designed for one part 37% acid and two parts 2%
> peroxide.  Since you're using a weaker acid and a stronger peroxide,
> you'll have to figure out the new ratios, but it will probably end up
> being two parts acid to one part peroxide.

That suits me fine -- it's easier to get the acid in large quantities 
than the peroxide.

 > Never add peroxide to acid!
>    Always add acid to peroxide.

Yep, I've heard the old saying:
"Add acid to water, just like you ought to!"

Acid + water is an exothermic reaction, just like mixing FeCl3 granules. 
Throw water into acid and you get localised boiling, fizzing and hot 
steam... not really a good thing when dealing with corrosive substances.

> If you want to skip right to CuCl, I found that about half a pound of
> copper converts 3 liters of CuCl etchant.

So just chuck 1lb of copper pipe into the tank, and leave it with the 
air pump running?

You mention that the peroxide degrades in about a week, am I right in 
thinking this only applies to the HCl+H2O2 etchant, i.e. by the time 
it's CuCl, this is of little effect?

Do sealed bottles of peroxide degrade in the same way, or just open bottles?

I suspect I'll probably buy enough peroxide for two attempts, i.e. 
2-litre tank, 3 parts chem = 660ml a time, or 1.2l peroxide, and a 
5-litre bottle of brick cleaner (about the cheapest way to buy it). Just 
in case I screw something up...!

Thanks,
-- 
Phil.
ygroups@...
http://www.philpem.me.uk/