Homebrew PCBs

OK, I made up some of this stuff...2/3 peroxide and 1/3 acid, and it 
worked fine the first time. Nice light green color when done, so I set 
it aside in a sealed container for next time. 2 days later, I went to 
etch again, and the stuff is dead. Peroxide doesn't reactivate it, and 
the color is still light green. What am I missing?

thanks, Jim

Good Heavens!
The brew is so inexpensive, why try to save it?
After etching the PCB, just neutralize the brew with sodium bicarbonate 
and flush it down the drain.
Mix just enough to do a one-shot etch. Use a fresh brew for each job,
unless you are etching several small boards in succession.

Roland F. Harriston, PD



Jim Klitzing wrote:

>
> OK, I made up some of this stuff...2/3 peroxide and 1/3 acid, and it
> worked fine the first time. Nice light green color when done, so I set
> it aside in a sealed container for next time. 2 days later, I went to
> etch again, and the stuff is dead. Peroxide doesn't reactivate it, and
> the color is still light green. What am I missing?
>
> thanks, Jim
>
>

2/3 peroxide lets me think this was low concentration medical stuff.
With that there is almost no way to continue using the etchant, since
it adds too much water.

Other than that, the etchant should just keep right on working when
H2O2 (and HCl) is added.
If you can get higher concentration H2O2 (>20%) there is no need to
throw it away.

ST

On Mon, Jun 30, 2008 at 9:13 PM, Jim Klitzing <wb6myc@...> wrote:
> OK, I made up some of this stuff...2/3 peroxide and 1/3 acid, and it
> worked fine the first time. Nice light green color when done, so I set
> it aside in a sealed container for next time. 2 days later, I went to
> etch again, and the stuff is dead. Peroxide doesn't reactivate it, and
> the color is still light green. What am I missing?
>
> thanks, Jim
>
>
> ------------------------------------
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>
>

The peroxide decomposes into water and oxygen real fast, so "some"
peroxide will rejuvenate it a little, but consider that you started
with *2/3* peroxide - a little isn't going to make it as good as new.

I have an older hcl/h202 solution that I'm slowly turning into a CuCl
solution and the etch time is on the order of an hour or so, but it
does make progress.  I run the bubbler to recharge the cucl, which
evaporates some of the water, making room for more peroxide when I get
back to it.

However, I'm guessing my 3 liter tank will need at least a pound of
copper (16 12"x12" boards) to get to the "sweet spot".

DJ Delorie wrote:
> However, I'm guessing my 3 liter tank will need at least a pound of
> copper (16 12"x12" boards) to get to the "sweet spot".
> 

A pure CuCl2/HCl etchant can work with fairly wide range of copper 
concentrations. From memory the copper should be in the 70 to 120g/l 
range for optimum etch speed. So your 3L tank needs 210 grams (1 pound). 
Ok your right. You can dump in 1 pound of copper pipe or old electrical 
cable , and let it bubble for a few days. Just keep the HCl additions so 
it stays acidic during this time. It goes green when finished.

Adam Seychell <a_seychell@...> writes:
> A pure CuCl2/HCl etchant can work with fairly wide range of copper 
> concentrations.

Your web page says 1.2 to 1.4 specific gravity, hence my "check my
math" posting - to get 3l (3kg) of water to 1.2 sg, you need 20% more
mass, or another 600g

> You can dump in 1 pound of copper pipe or old electrical cable , and
> let it bubble for a few days. Just keep the HCl additions so it
> stays acidic during this time. It goes green when finished.

Based on how the tank is acting, I think the acid is still OK - if I
put copper oxide (wire over a gas stove flame) in it, it eats the
oxide off pretty quickly.  It's also getting darker green over time,
as I etch more boards.  What I've been doing is adding H2O2 to bring
it back up to where it's supposed to be (i.e. to counteract
evaporation) when I etch boards.  I tried titration once, but didn't
have enough copper in it to act as an indicator then.

I did a board today and it took 40 minutes.  At least, I remembered to
go check it at 40 minutes and it was done ;-) I also positioned it so
that the air bubbles actually hit the board, not just went past it.

Actually, my problems over the weekend were due to *over* etching.
I'm still experimenting with the photomask.  So far I've learned to
match up line/space rules across a panel so that the etch times match.
Maybe I'll cut up the panel after exposure so I can etch them
individually.  Small traces with big spaces were etched away while
waiting for a board with small spaces to etch.  It never did, even
after 2 hours.  Maybe floating it over FeCl would result in a more
consistent etch.

You have a lot of patience!

 

I have not etched any PCBs for a few years but I used to do quick single
sided ones for prototypes and fixtures.

 Smaller boards I used to etch in round glass dish on a hotplate with a
magnetic stirrer for fast agitation.  With the agitation and hot FeCl it
took just a few minutes to do a board.  I turned the board upside down and
held it in place with a suction cup.

 

For bigger boards I used a rocker with hot FeCl.   I started to build a
spray etcher but got too busy to finish it.

 

To get good results I think it is important to have lots of agitation to
avoid the etchant to locally saturate.

Bertho

From: DJ Delorie   Sent: Tuesday, July 01, 2008 20:16
-àsinip
I did a board today and it took 40 minutes. At least, I remembered to
go check it at 40 minutes and it was done ;-) I also positioned it so
that the air bubbles actually hit the board, not just went past it.

Actually, my problems over the weekend were due to *over* etching.
I'm still experimenting with the photomask. So far I've learned to
match up line/space rules across a panel so that the etch times match.
Maybe I'll cut up the panel after exposure so I can etch them
individually. Small traces with big spaces were etched away while
waiting for a board with small spaces to etch. It never did, even
after 2 hours. Maybe floating it over FeCl would result in a more
consistent etch.



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

"Bertho Boman" <boman01@...> writes:
> You have a lot of patience!

Well, if I'm in a hurry I can hand etch with hot FeCl and a sponge in
under a minute.  For now, with the CuCl, I just put it in and go do
something else.  Usually work ;-)

Once the CuCl bath is fully built, it should etch in a few minutes.

> To get good results I think it is important to have lots of
> agitation to avoid the etchant to locally saturate.

The tank has an air bubbler in it to keep things moving around.  I
might build a new bubbler rig to get more even air bubbles, and on
both sides of the board.

Meanwhile I move the board around every 10 minutes or so.

Hi.  With the FeCl and "sponge technique", what do U use for resist?
Are U the pre-sensitized pcb??  thanx   T

--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:

>
> "Bertho Boman" <boman01@...> writes:
> > You have a lot of patience!
> 
> Well, if I'm in a hurry I can hand etch with hot FeCl and a sponge in
> under a minute.  For now, with the CuCl, I just put it in and go do
> something else.  Usually work ;-)
>

"TonyB" <tbarros@...> writes:
> Hi.

Hi.

> With the FeCl and "sponge technique", what do U use for resist?

Please use whole words, not leet-speak.

I haven't tried using the sponge technique with photoresist yet, but I
have used it with toner transfer.  Do do this, you need to use a
coating film to protect the toner from the abrasion.  I use Pulsar's
green film for this.  Photoresist should be usable as-is if it's
adhered to the board sufficiently that the sponge won't abrade it off.

> Are U the pre-sensitized pcb??

No, I'm not the pre-sensitized pcb.

So far, all I've used is toner transfer, or dry film photoresist which
I apply myself.  I use Adam's wet lamination technique.

> > Tony wrote:
> > With the FeCl and "sponge technique", what do U use for resist?

> DJ wrote:
> Please use whole words, not leet-speak.

Isn't that 1337-5P33K

Andrew wrote:
> Isn't that 1337-5P33K

More like txt-speek. SMS text messaging tends to warp the mind...

-- 
Phil.
ygroups@...
http://www.philpem.me.uk/