Homebrew PCBs

I've got a somewhat new tank of HCl etchant that I've used a few
times, but it's mostly been sitting for a while.  It's only pale
green, but it's emerald not brownish.  My test boards (one just
scrubbed copper as a control) have been in it for 40 minutes now.
It's warm and the bubbler is running, I even added a shot of peroxide
ten minutes ago.  It etched real quick the first time I used it, when
it was fresh.

What's the most likely cause of this sluggishness?  What could I try
doing?  Things to test?

I was thinking of making some copper oxide (the wire+heat trick) and
try to get the solution darker, but I'd rather not put too much copper
in if there are simpler ways.

----- Original Message ----- 

From: "DJ Delorie" <dj@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, June 17, 2008 8:19 PM
Subject: [Homebrew_PCBs] sluggish etchant


> 
> I've got a somewhat new tank of HCl etchant that I've used a few
> times, but it's mostly been sitting for a while.  It's only pale
> green, but it's emerald not brownish.  My test boards (one just
> scrubbed copper as a control) have been in it for 40 minutes now.
> It's warm and the bubbler is running, I even added a shot of peroxide
> ten minutes ago.  It etched real quick the first time I used it, when
> it was fresh.
> 
> What's the most likely cause of this sluggishness?  What could I try
> doing?  Things to test?

What concentration is the H2O2 you are using?

Leon
--
Leon Heller
Amateur radio call-sign G1HSM
Yaesu FT-817ND and FT-857D transceivers
Suzuki SV1000S motorcycle
leon355@...
http://www.geocities.com/leon_heller

"Leon" <leon355@...> writes:
> What concentration is the H2O2 you are using?

It was the usual 2 parts 3% H2O2 to 1 part 37% HCl.  But like I said,
it's been sitting for a while.

----- Original Message ----- 

From: "DJ Delorie" <dj@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, June 17, 2008 8:52 PM
Subject: Re: [Homebrew_PCBs] sluggish etchant


>
> "Leon" <leon355@...> writes:
>> What concentration is the H2O2 you are using?
>
> It was the usual 2 parts 3% H2O2 to 1 part 37% HCl.  But like I said,
> it's been sitting for a while.

3% is too weak, unless you make up fresh etchant each time. I use ferric 
chloride, it's much less trouble.

Leon
--
Leon Heller
Amateur radio call-sign G1HSM
Yaesu FT-817ND and FT-857D transceivers
Suzuki SV1000S motorcycle
leon355@...
http://www.geocities.com/leon_heller

the bubbler running will provide for some of the needed O2.
perhaps a little more HCl is needed, it also fumes out...



--- On Tue, 6/17/08, DJ Delorie <dj@...> wrote:

> I've got a somewhat new tank of HCl etchant that
> I've used a few
> times, but it's mostly been sitting for a while. 
> It's only pale
> green, but it's emerald not brownish.  My test boards
> (one just
> scrubbed copper as a control) have been in it for 40
> minutes now.
> It's warm and the bubbler is running, I even added a
> shot of peroxide
> ten minutes ago.  It etched real quick the first time I
> used it, when
> it was fresh.
> 
> What's the most likely cause of this sluggishness? 
> What could I try
> doing?  Things to test?
> 
> I was thinking of making some copper oxide (the wire+heat
> trick) and
> try to get the solution darker, but I'd rather not put
> too much copper
> in if there are simpler ways.

The problem with air bubbling is that you need enough CuCl in there to
finish the board (and then some). Otherwise you'd need to re-generate
during etching, which i think would be very slow. The advantage of
H2O2 is that any excess stays in the tank, at least for a short while,
available to immediately regenerate any CuCl. This means you can etch
a board even if there is not enough CuCl in the tank, and it allows to
"build up" CuCl by etching PCBs (which i would consider very
impractical with air bubbling alone).

ST

On Tue, Jun 17, 2008 at 11:30 PM, Herbert E. Plett <cachureos@...> wrote:
> the bubbler running will provide for some of the needed O2.
> perhaps a little more HCl is needed, it also fumes out...
>
>
>
> --- On Tue, 6/17/08, DJ Delorie <dj@...> wrote:
>> I've got a somewhat new tank of HCl etchant that
>> I've used a few
>> times, but it's mostly been sitting for a while.
>> It's only pale
>> green, but it's emerald not brownish.  My test boards
>> (one just
>> scrubbed copper as a control) have been in it for 40
>> minutes now.
>> It's warm and the bubbler is running, I even added a
>> shot of peroxide
>> ten minutes ago.  It etched real quick the first time I
>> used it, when
>> it was fresh.
>>
>> What's the most likely cause of this sluggishness?
>> What could I try
>> doing?  Things to test?
>>
>> I was thinking of making some copper oxide (the wire+heat
>> trick) and
>> try to get the solution darker, but I'd rather not put
>> too much copper
>> in if there are simpler ways.
>
>
>
>
>
> ------------------------------------
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>
>

"Herbert E. Plett" <cachureos@...> writes:
> perhaps a little more HCl is needed, it also fumes out...

Follow-up:

CuCl concentration is below 1.2 (which I figured).

Acid seems high enough.  I heated some copper wire to get Copper
Oxides, and the etchant dissolved that just fine, leaving a bright
pinkish copper behind.  I did that a few times to get more copper into
the tank, and then left the wire in there.  Perhaps by the time I get
around to fiddling with it again it will be more usable, otherwise
I'll put in more H2O2.

I did make up some NaOH solution for titration but it neeeds time to
fully dissolve.

DJ Delorie wrote:
> "Herbert E. Plett" <cachureos@...> writes:
>> perhaps a little more HCl is needed, it also fumes out...
> 
> Follow-up:
> 
> CuCl concentration is below 1.2 (which I figured).
> 
> Acid seems high enough.  I heated some copper wire to get Copper
> Oxides, and the etchant dissolved that just fine, leaving a bright
> pinkish copper behind.  I did that a few times to get more copper into
> the tank, and then left the wire in there.  Perhaps by the time I get
> around to fiddling with it again it will be more usable, otherwise
> I'll put in more H2O2.
> 
> I did make up some NaOH solution for titration but it neeeds time to
> fully dissolve.
> 
NaOH should dissolve in < 10 minutes even in cold temperatures. Usually 
the heat generated speeds up the processes to under a minute.
Are you sure its NaOH ?
Does it spoon of NaOH power placed on exposed surface absorb water from 
the atmosphere in 1/2 day to a liquid ?
If not then it may be mostly Na2CO3

Adam Seychell <a_seychell@...> writes:
> Are you sure its NaOH ?

The jar says "warning: contains sodium hydroxide".  It's pure lye.  It
dissolved, it just didn't dissolve *immediately*.  Most did, but there
was some leftover at the bottom that took a bit longer.  I didn't need
it right away, so I just set it aside.  It's all dissolved now.

Hi, Your ratio is right.
but, dont add anymore peroxide. Remember, peroxide is mostly water,
and that will stall the etching. The best way to tell what you need
whether it be more acid or peroxide is to do a titration test.
heres a link:

http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/index.html#analysis_acid

This will tell you how much acid to add to the mix to bring you back
to the 2:1 ratio

hope this helps!
Joe