Homebrew PCBs

Thanks.

When you say 'bubble air through it' you mean like w/ a fish tank air pump w/ those 1 way valves?  Do I know how much air I need based off the color and if so, what color am I looking for?  In the past I had some weak acid and it turned teal blue but this stuff is staying bright lime green.

Also, yes, I did heat it up.  I was using a small 'tupperware' dish in a larger one that was filled w/ water ~120-140F.

When you say a bit slower, I assume you mean than the first batch and not my slow 45min marathon etch?

Bob

--- In Homebrew_PCBs@yahoogroups.com, Harvey White <madyn@...> wrote:
>
> On Sun, 28 Oct 2012 05:21:57 -0000, you wrote:
> 
> >I have been using H2O2 from the pharmacy / Muriatic Acid combo, 2:1 - works well and is easy to get, but it doesn't work after the initial use.  It seems every etch, I need to make a new batch.  The etchant turns into a bright lime green color on the first etch and it does what I need to pretty quick and it seems like there is decent activity - bubbles which only happens on the first time use, after that maybe bubbles when I first put in the pcb/Cu but they go away very quickly.
> >
> >After use, I will put the solution in a clear, sealed glass container and even if I use it the next day, after I start, 45min later my etch is still not done, so I dispose of it and make a new batch at which time I am done in 15mins.
> >
> >What am I doing wrong or where is the mixture out of balance?  Again, I just did an etch this evening and had to make a new batch, which is now a bright lime green color.
> 
> The etchant uses the oxygen from the peroxide to enable the etching.
> To continue to etch with that solution, you need to bubble air through
> it.  It will also help to heat the solution to 100 degrees F or so.
> 
> The solution will gradually turn a darker green.  If it turns olive
> (IIRC), then the chemistry is out of balance.  The peroxide provides
> oxygen only for the first day or so, at which point the etchant turns
> into a CuCl etchant, which works very well, is a trifle slower, but
> never wears out.  I think that there's a good review of this chemistry
> in the group archives, which explanation is better than mine.
> 
> You'll find that if you add some relatively concentrated peroxide to
> the etchant, it will start to work the way you expect, but the word is
> concentrated.  Not really needed.
> 
> Some people take the peroxide etchant mix and deliberately add copper
> to it, producing the CuCl etchant to start with.
> 
> You will eventually have to add either Muriatic acid to the mix to
> replace the chloride ion, again, IIRC.
> 
> Harvey
> 
> >
> >Thanks in advance,
> >Bob
>