Homebrew PCBs

Phil,

I use an muriatic (hydrochloric) acid and peroxide etchant in a tray. I mix
the etchant just before use, and since the combination is *exothermic*, it
heats itself long enough to get the job done. I have used persulfate
etchants in trays, but the solution does have to be heated. This can be
done, as you suggest, by mixing the persulfate into *hot* water. I say hot
because as persulfate goes into solution, there is an *endothermic*
reaction--it cools down.

By the time it's fully dissolved it's still warm enough to etch,
particularly since it is a fresh solution and etching times will therefore
be short. If you reuse the etchant, you can always heat it carefully in a
microwave. It will also help to preheat the tray and pcb in hot tap water
so they don't draw heat from the etchant.

I suppose it's possible you got some bad persulfate on your second try. I
haven't used it for some time now, so I don't know good sources. I suspect,
though, that MG Chemicals would have good quality material.
http://www.mgchemicals.com/products/prototyping-and-circuit-repair/prototyping/
.

73,

Todd
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K7TFC / Medford, Oregon, USA / CN82ni / UTC-8
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QRP (CW & SSB) / EmComm / SOTA / Homebrew / Design


On Tue, Feb 19, 2013 at 11:22 PM, phil.quinton@ymail.com <
phil.quinton@...> wrote:

> **
>
>
>
>
> Todd,
>
> Thank you for the advice.
>
> If you use a tray for etching, how do you keep the temperature up for the
> sodium persulphate?
>
> Or is it just a case of getting the water warm before you mix in the
> etchant?
>
> It's possible that the agitator is too aggressive, especially as the etch
> time is taking so long.
>
> Can there be a difference in the quality of the sodium persulphate? The
> current batch is from a difference source to the very first etching.
>
> Thanks again,
> Phil.
>
>
> --- In Homebrew_PCBs@yahoogroups.com, "Todd F. Carney" wrote:
> >
> > Either ammonium persulfate or sodium persulfate is used by commercial pcb
> > manufacturers. They do not use ferric chloride, not for decades. Only
> > hobbyists use the stuff. I'm using a peroxide-muriatic acid-sodium
> chloride
> > etchant. It's very cheap, and the chemicals are available either in a
> drug
> > store or at places such as Home Depot (for the acid). I use it
> "one-shot."
> > I use just enough to do the board I'm etching and then toss it away. It's
> > that cheap. This way, It works the same way--etch times, etc.--every
> time I
> > use it.
> >
> > 73,
> >
> > Todd
> > ----------------------------------------------------------
> > K7TFC / Medford, Oregon, USA / CN82ni / UTC-8
> > ----------------------------------------------------------
> > QRP (CW & SSB) / EmComm / SOTA / Homebrew / Design
> >
> >
> > On Tue, Feb 19, 2013 at 9:12 PM, tda7000 wrote:
> >
> > > **
>
> > >
> > >
> > >
> > >
> > > I have used the toner transfer method with the laminator described
> here:
> > > http://ultrakeet.com.au/write-ups/superfuser
> > >
> > > I have not used Press-n-peel blue, just magazine paper. However I have
> not
> > > had undercutting (that I ever noticed!). I used old Ferric Chloride and
> > > later on the Hydrochloric acid and Hydrogen Peroxide mixture. Both
> worked
> > > great.
> > >
> > > http://ultrakeet.com.au/write-ups/etchantComparison he describes
> Ammonium
> > > Persulphate as being much worse than Ferric Chloride. I have never used
> > > Ammonium Persulphate.
> > >
> > > I don't know if it's any different to Sodium Persulphate in terms of
> > > undercutting, but if his article has any truth behind it I would
> probably
> > > try something else.
> > >
> > >
> > > --- In Homebrew_PCBs@yahoogroups.com, "phil.quinton@" wrote:
> > > >
> > > > Hi,
> > >
> > > First post, hopefully one of many..
> > >
> > > To cut a long
> > > > story short, I'm having problems *after* etching with Sodium
> > > > Persulphate
> > >
> > >
> > >
> > > In short, it appears to be etching *under* the
>
> > > > toner somehow.
> > >
> > > My guess is that the etch tank is no
> > > > longer getting to the right temperature ( ~ 45 degrees ) and I'm
> etching
> > > > too long with the agitator on. I'm going to get myself a temperature
> > > > probe to confirm.
> > >
> > > Has anyone had a similar experience ( Etch
> > > > looking fine until the toner is removed )?
> > >
> > > Thanks in
> > > > advance,
> > > Phil.
> > >
> > > >
> > >
> > >
> > >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>
>  
>


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