Homebrew_PCBs

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@g...> wrote:

>
>
> > Wow really small quantity !!! last question, Can it be regenarate

for

> > ever , or should be dispose after some H2O2 addition ???
> >
> > Thanks
> >
> > Bruno
>
> You can use it indefinitely. Of course HCl is also used up, so you

need to

> add that too after a while. You can either go by feel and add when

it

> doesn't help to add H2O2, or you see any blue sludge on the PCB, or

you

> can look in the links section on how to measure the molarity of HCl

in the

> etchant. Look for the method with the two eyedroppers it is the

only one

> sufficiently simple IMO. You might also want to get a hydrometer.

It is

> used to measure density (amount of copper per volume). You can get

one

> cheap and easy in the car tools store, it is used to measure

battery

> fluid. Should cost well under 10$. Go for the type with the

swimming

> hydrometer in a large glass pipette, not the small plastic

rotating

> pointer one. But that's really only if you are curious about the

etchant,

> it is not a requirement to make it work.
>
> Now if we only keep to add stuff to the etchant it will of course

grow in

> volume. This is very slow and is good because it dilutes the copper

in

> more etchant, otherwise you will reach a point where the specific

gravity

> gets too high. Should you get too much etchant at one point you'll

have to

> dispose of some, but unless you make really many boards regularly

the

> growth is barely noticeable.
>
>
> You will find if you keep using your etchant it will gradually turn

from

> HCl+H2O2 etching to CuCl etching, that means instead of "instantly"

using

> and needing H2O2 to etch the H2O2 can be used to regenerate

existing CuCl

> in the etchant. What that means for you is that once there is

enough CuCl

> you do not necessarily need to add H2O2 each time. You only add it

when

> the etchant turns from a bright green to a darker, brownish color.

If

> there is enough bright green regenerated etchant for the board

there you

> do not need to add any H2O2, even if you last etched months ago.

OTOH it

> will not help to add too much H2O2 - once all the etchant is bright

green

> it does no good and will just decompose to useless oxygen that has

nothing

> to regenerate and is released into the air.
>
>
> *********
>
> > If it fizzes, you added too much. It won't actually do any harm

if youdo

> > put too much in. I normally fill the cap of the bottle up and

tipthat

> > in. It seems to be about right for my tank.
> > Les
>
> if it fizzes it creates loads of nasty fumes that are corrosive.

It's

> definitely too much if it does that.
>
> ST
>

Thanks a lot for all these info !!!!, right now mine is bright clear
green but etch really slowly, so i'll get H2O2 30% !!!!

Thanks

Bruno