Homebrew PCBs

On Fri, 2009-07-03 at 09:46 +1000, Adam Seychell wrote:

> A nice effort on finding a suitable etchant for metallic etch resist.
> I 
> tried persulfate but that attacked tin enough to make it unreliable. 
> From your description the nitric-sulfuric mix sounds like the best 
> hobby etchant compatible with pure tin metallic resist. The alkaline 
> ammonia chloride type works great on tin resists, not even affecting
> the 
> mirror shine tin surface. The downside is the need for regular
> ammonia 
> replenished due to NH3 loss. This etchant is regenerated with
> ammonium 
> chloride salt, concentrated aqua ammonia, water, and air. Alkaline 
> ammonia chloride etches relatively fast, up there with fresh FeCl3.
> 
> Have you tried etching a mix of concentrated HCl and HNO3, also known
> as 
> Aqua Regia ? That should give you a run for your money.
> 

Funny! Yes is a crazy thing. But is PATENTED for pure tin metallic
resists! 

Like i said is like the peroxide-sulfuric etchant, and from a searchable
post from you, you know about peroxide-sulfuric with phosphoric acid and
additives to work as metallic resist etchant (And from you i know that
the tin don't end looking so good). I didn't said it explicitly but it
also uses phosphoric acid for tin resits (along with additives).

The thing etches copper, and i get a big amount of copper sulfate
easily. But is almost like Aqua regia that even etches gold. The toner
is there just to give the bath a black color :>

I found the sulfuric-nitric etchant searching for oxidants for a
sulfuric based etchant. You use a very good etchant and only at the 2rd
time i read it, i noted you use it outside. You are also the only author
I found with anything from ammonia sulfate etch. Your Ammonia MEA report
is a very clever way to get ride ammonia smell.

You know patents better than me, the ones i talk about are uspo 4632727
and 4497687.

But yes, is obvious what i will end using... Very Thanks!

>