Homebrew_PCBs

Is there any issues with mixing etching solutions

From 30% HCL / 30% H2O2 to the right concentrations/ ratios

And mix together and store that way ?

Or is there an issue with it becoming weaker just sitting around ..



Randy - N2CUA



[Non-text portions of this message have been removed]

I get about 2 days out of a HCL/H2O2 solution. The problem seems to be that the H2O2 breaks down into water very quickly. I've even tried storing it in an old brown H2O2 bottle (light breaks it down very quickly), but it didn't seem to help. I mix it up when I need it, then put the spent solution in a safe bottle for proper disposal later.

You can also make your own cupric chloride for etching which lasts a long time (with occasional maintenance). There are many tutorials and how-tos to get it working but it's a very involved process.

--- In Homebrew_PCBs@yahoogroups.com, "N2CUA" <n2cua@...> wrote:
>
> Is there any issues with mixing etching solutions
>
> From 30% HCL / 30% H2O2 to the right concentrations/ ratios
>
> And mix together and store that way ?
>
> Or is there an issue with it becoming weaker just sitting around ..
>
>
>
> Randy - N2CUA
>
>
>
> [Non-text portions of this message have been removed]
>

Lets see if I can remember the redox stuff from chemistry.

The HCL/H202 is just the starter, the real etchant is the Cupric Chloride (+2 oxidation state)you eventually end up with. Initially the HCL/H202 etch the copper off the board forming Cuprous ions (+1 oxidation state)in the solution. Then more H202 is added or O2 is bubbled through the solution to oxidizes the Cuprous ions back to Cuperic ions. As the quantity of copper in solution increases more HCL must be added to keep the chloride ions in balance with the ever increasing copper in solution. You actually make more etchant with every board etched. There has been extensive postings about this process and how to replenish and regenerate the etchant. My understanding is that 3% H202 adds too much water and dilutes your etchant. For best results use 30% if you can find it.

Cu + CU++ ---> 2CU+ the etching equation

http://www.pcbfab.com/chemistry-of-the-cupric-etch

Craig

--- In Homebrew_PCBs@yahoogroups.com, "N2CUA" <n2cua@...> wrote:
>
> Is there any issues with mixing etching solutions
>
> From 30% HCL / 30% H2O2 to the right concentrations/ ratios
>
> And mix together and store that way ?
>
> Or is there an issue with it becoming weaker just sitting around ..
>
>
>
> Randy - N2CUA
>
>
>
> [Non-text portions of this message have been removed]
>

Some snippage ...

You can get "40 weight" peroxide, which I believe is 10%, from Sally Beauty Supply. It works fine.

They have a lot of other interesting chemicals and devices there too.

73
Jim N6OTQ

>________________________________
> From: designer_craig <cs6061@...>
>To: Homebrew_PCBs@yahoogroups.com
>Sent: Thursday, May 9, 2013 12:28 PM
>Subject: [Homebrew_PCBs] Re: etching solutions
>
>
> For best results use 30% if you can find it.
>
>Cu + CU++ ---> 2CU+ the etching equation
>
>http://www.pcbfab.com/chemistry-of-the-cupric-etch
>
>Craig
>
>

[Non-text portions of this message have been removed]

--- In Homebrew_PCBs@yahoogroups.com, "N2CUA" <n2cua@...> wrote:

> Is there any issues with mixing etching solutions
>
> From 30% HCL / 30% H2O2 to the right concentrations/ ratios
>
> And mix together and store that way ?



On Thu, May 9, 2013 at 10:28 AM, designer_craig <cs6061@...> wrote:

> **
>
> The HCL/H202 is just the starter, the real etchant is the Cupric Chloride
> (+2 oxidation state)you eventually end up with. Initially the HCL/H202 etch
> the copper off the board forming Cuprous ions (+1 oxidation state)in the
> solution. Then more H202 is added or O2 is bubbled through the solution to
> oxidizes the Cuprous ions back to Cuperic ions. As the quantity of copper
> in solution increases more HCL must be added to keep the chloride ions in
> balance with the ever increasing copper in solution. You actually make more
> etchant with every board etched. There has been extensive postings about
> this process and how to replenish and regenerate the etchant. My
> understanding is that 3% H202 adds too much water and dilutes your etchant.
> For best results use 30% if you can find it.
>

I use the 30% HCL ("muriatic acid") from Home Depot (~$12/gallon) and the
drug-store-variety 3% peroxide. I mix up only 2oz (~50ml) at a time for
boards up to 4x6 inches (the largest I ever do), and I use it *one shot*
and then dispose of it (more on that later). This provides very consistent
results, and I don't have to wonder about shelf life or strength. I learned
this one-shot chemistry technique in photography. I'd guess I spend about
10 cents on each shot.

Responsible disposal is, of course, an issue. At first, instead of dumping
it down the drain, I dumped in into a five-gallon bucket filled with wood
shavings. My plan was to keep that bucket of shavings for as long as
possible before triple bagging them for the land fill. But then someone on
the list chewed my ass for creating more toxic waste. His alternative was
to neutralize the solution in such a way that the copper is bound-up in a
safe compound. I do not now recall his simple process (I haven't done any
etching since then), but searching this list for "peroxide" and "muriatic"
and "wood shavings" will turn up his postings and my bloody ass.

Best,

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


[Non-text portions of this message have been removed]

"Todd F. Carney / K7TFC" <k7tfc@...> writes:

> Responsible disposal is, of course, an issue.

The "waste" your trying to dispose of, is itself an etchant. Save it,
eventually you'll have a Cupric chloride etchant that doesn't need to be
disposed of at all.

I made my etchant by mixing HCl and H2O2 in a big container, then
throwing in about half a pound of scrap copper and an air hose. The
"waste" is a nice emerald green CuCl etchant that I've been using ever
since.

DJ,

Thanks. What are your typical etching times and temperature for, say, 1oz
copper?

Best
,

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

On Thu, May 9, 2013 at 12:12 PM, DJ Delorie <dj@...> wrote:

> **
>
>
>
> "Todd F. Carney / K7TFC" <k7tfc@...> writes:
> > Responsible disposal is, of course, an issue.
>
> The "waste" your trying to dispose of, is itself an etchant. Save it,
> eventually you'll have a Cupric chloride etchant that doesn't need to be
> disposed of at all.
>
> I made my etchant by mixing HCl and H2O2 in a big container, then
> throwing in about half a pound of scrap copper and an air hose. The
> "waste" is a nice emerald green CuCl etchant that I've been using ever
> since.
>
>
>


[Non-text portions of this message have been removed]

"Todd F. Carney / K7TFC" <k7tfc@...> writes:

> Thanks. What are your typical etching times and temperature for, say, 1oz
> copper?

I don't maintain the solution as well as I should. Sometimes it's as
fast as 4 minutes, sometimes as long as 20. Depends on temperature, and
I'm probably off on the chemistry a little.

See http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/

I was able to locate 29% H2O2 at the following location:

http://www.finlandiapharmacyonline.com/products/O2XY%252dPLUS-Food-Grade-Hydrogen-Peroxide-29%25.html

I am lucky enough to live in Vancouver so just went directly to their store.

Jim VE7SU

--- In Homebrew_PCBs@yahoogroups.com, Jim <n6otq@...> wrote:
>
> Some snippage ...
>
> You can get "40 weight" peroxide, which I believe is 10%, from Sally Beauty Supply. It works fine.
>
> They have a lot of other interesting chemicals and devices there too.
>
> 73
> Jim N6OTQ
>
>
>
> >________________________________
> > From: designer_craig <cs6061@...>
> >To: Homebrew_PCBs@yahoogroups.com
> >Sent: Thursday, May 9, 2013 12:28 PM
> >Subject: [Homebrew_PCBs] Re: etching solutions
> >
> >
> > For best results use 30% if you can find it.
> >
> >Cu + CU++ ---> 2CU+ the etching equation
> >
> >http://www.pcbfab.com/chemistry-of-the-cupric-etch
> >
> >Craig
> >
> >
>
> [Non-text portions of this message have been removed]
>