Homebrew PCBs

I'll guess that if you add more H2O2, it will work again.  With the 
impurities from the etching and the natural tendency of H2O2 to go to 
H2O and O2, I'd bet that's your problem.

sam_jfs wrote:
> --- In Homebrew_PCBs@yahoogroups.com, "Jamie Lyon" <aeonflame@...> wrote:
>   
>> Hi all,
>>
>> I'm currently etching with Ammonium Persulfate, but having to heat it
>> up isn't very easy, so I want to give etching with hydrochloric acid +
>> hydrogen peroxide a go.
>>
>> I've managed to get hold of the acid in the form of brick cleaner, it
>> doesn't specify the percentage, but I'm assuming it's somewhere around
>> 30%, which seems to be standard.
>>
>> The hydrogen peroxide however I had quite an issue getting hold of
>> (I'm in the UK), I've managed to get some medical grade (3%) stuff
>> from a local supermarket, however it mentions other extra contents on
>> the label, phosphoric acid & phenacetin. I'm not sure what the volume
>> of those additives are, as it doesn't mention it on the label. Would
>> they possibly cause an issue? I don't want it blowing up in my face
>> when I mix it :)
>>
>> Finally, I've seen several mixes on the net -- with the medical grade
>> peroxide, does 2:1 peroxide:acid sound about right?
>>
>> Many thanks,
>> Jamie
>>
>>     
>
> I use Muriatic acid and H2O2 ( medical grade 3% too ) with good
> results. The only problem is, after some days i can\ufffdt really etch with
> it, i must throw it away and make a new one, i don\ufffdt know why, i don\ufffdt
> understand chemistry ...
> I use 3:1 ( 3 of H2O2 and 1 of Muriatic acid ), it\ufffds quite fast, about
> 5 to 10 minutes at room temperature (+/- 20\ufffdC ).
>
> Sam
>
>
>
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