Homebrew PCBs

Stefan Trethan wrote:

> 
> Well, one would have to dig out the discussion from a few years ago to
> see the details.

I should do it too, but in another moment off non confirmed comments; if
i read it right or if is still used the stabilizer for peroxide
decomposition are phenol compounds. If Phenolsulfonic acid is used
should stabilize peroxide and protect tin. If so makes the think&tinker
stabilizer useful in both ways. Since non ammonia etchants compatible
with tin resist use phosphoric acid and derivatives to protect tin. (no
experience just read it).
I think that in 'printed circuits handbook' is written that adding
phosphoric acid to ammonia persulfate makes it tin compatible i will try
to check that too. 

The last off the patents i mentioned shows nitric as oxidizer in small
amount on a mixture of sulphuric and phosphoric acid (among other
stuff), making a tin compatible etchant. Since is easier to get nitric
acid than high concentration peroxide it may be a nice candidate. But
although i have it all in my house i never try it...