Homebrew PCBs

I use both FeCl3 and Acid/H202 etchant. Each has its good points as 
well as its hazards. In either case, protective safety equipment must 
be used.

FeCl3 is a "milder" and "safer" etchant to handle. Yes, it does stain 
just about everything, but there is usually very little serious 
damage. On the other hand, Muriatic acid / H202 is extremely damaging 
to just about everything, including skin.

We all tend to become a little too familiar with the process and get 
sloppy. I have had my share of stains and burns too. I definitely 
prefer the FeCl3 stain.

When I do an acid etch, I wear goggles and rubber gloves. I have the 
etchant tank in a second containment tray. I also have a half kilo of 
baking soda handy as well as running water. After finishing, I dust 
everything with baking soda and keep adding baking soda to any spots 
that fizz. Then carefully wash everything down.

The acid etching process does generate heat and bubbles. There can be 
a mist of etchant that is almost invisible. You will notice the 
effects, if not immediately, but in a very short period of time. Acid 
burns cause intense pain and heal very slowly. Fabric distegrates.

Do not underestimate the danger. Having a little "experience with 
acds and bases" in high school, does not adequately prepare you for 
proper use.

Be safe!

Myc
Industrial Chemist for 30 years


--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan" 
<stefan_trethan@...> wrote:
>
> On Sun, 25 Mar 2007 13:30:24 +0200, sam_jfs <Samuel_joao@...>  
> wrote:
> 
> > I use Muriatic acid and H2O2 ( medical grade 3% too ) with good
> > results. The only problem is, after some days i can´t really 
etch with
> > it, i must throw it away and make a new one, i don´t know why, i 
don´t
> > understand chemistry ...
> 
> 
> The reason is that the H2O2 is not stable in the etchant, it 
dissipates  
> into the air.
> You can rejuvenate the etchant with fresh H2O2, but the problem 
with the  
> 3% stuff is you would add too much water.
> If you can get 25 or 30% H2O2 you can use the same etchant forever.
> 
> ST
>