Homebrew PCBs

On Sun, 2009-06-28 at 17:00 +0000, Charles wrote:
> FCL is just too poisonous to the environment (imho it should be
> outlawed).

Repeating what others said, the pollutant is copper, and FeCl3 can hold
a big quantity of it. Since it has no regeneration people will drain it
with copper and that's the bad thing.
FeCl3 is used in water treatment facilities ( i think to remove metallic
ions from water by filtration or deposition) . I know a small boardhouse
that still stupidly uses it because can be bought at the local water
treatment facility. And they send the waste FeCl3 with all the copper to
incineration!

>  The reason im so cautious with this is ive played with 90% nitric and
> copper and breathed in the fumes and it was bad. Sickness, nausea and
> i could tell acidic fumes had done damage to my lungs and airway. That
> is from a good breath or two of the stuff, no more. I dont know the
> specifics but i bet the gaseous byproducts are similar or identical.

> Btw you think watching a fast etch is cool you should see what high
> grade nitric does to copper (and that is without an oxygen source).
> 

Nitric acid is an Oxidizing. The gas produced in the copper reaction is 
nitric oxide which is toxic. People shouldn't use it as copper etch has
already discussed here long time ago by Adam Seychell, its hazard toxic
and air pollutant. 
But in my quest for metallic resist compatible etchants i found one
using nitric acid which i experimented. It's basically the same stuff as
peroxide-sulfuric etchant, but using nitric acid as the oxidizer. Since
i can't find here hydrogen peroxide in more than 9% solution, but i get
nitric acid in 60% at less 1.70eur/liter, it seem a cheap etch with easy
copper electrowinnig has i wanted. In peroxide-sulfuric the solution
amount is always increasing, so you always need some disposal. But with
nitric acid it consumes water, and the mixture of nitric sulfuric can
regenerate one HNO3 molecule in each 3 spent while makes CuSO4, besides
the air pollutant nitric oxide seems a nice etchant. I made various
tests but, the nitric acid attacks the toner almost completely... I also
etch a copper piece an got an enormous amount of CuS04 freezing it. The
solution turn almost clear, so almost all copper is easily deposited.
Only now i found a source of pure tin (in Australia) and i still have to
try the phosphorous mixture with plated tin as resist.

What have you used as resist in the nitric etchant?

> Ive been EXTREMELY careful of fumes using this method and am going to
> CuCL exclusively. 

I also have bad stories with having CuCl etchant and HCl on the self on
the same room as hundred of tools and an CNC router 'in construction'.
Lets say you need to have very careful with your containers and
phosphoric acid can give a nice look again to your tools but can't give
back the polish of expensive  CNC parts. Ventilation and sealed
containers are mandatory. 


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