Homebrew PCBs

Hi all,

I know that I don't post much to this list and act mostly as a lurker, but I
recently tried something that I found on a website (that I am sure many, if
not most on this list have already come across).  This will probably end up
a fairly long email, and for that I kind of apologize, but for those that
don't know or never realized, it might be good.

We all know that etching is evil necessity if we wish to make our own
boards - even though many of us utilize mechanical etching via CNC, some
circuit densities don't make that possible unless you have a major high
dollar machine (which of course most of us can't afford).

Well, I, like many others, don't have easy access to etching chemicals -
either we pray that radio shack happens to have a bottle of the nasty stuff,
or we order from a supplier.

I came across a website that mentioned using a muriatic acid and hydrogen
peroxide mix to etch boards.  This interested me as it would greatly reduce
the cost of a batch of etchant, and would be much easier to obtain
(considering you can get muriatic acid at local hardware stores.

First a warning:  This stuff is major dangerous.  if you think ferric
chloride is bad, this stuff makes ferric chloride practically look like
water.  Do not attempt to use this stuff if you don't have a very healthy
respect for chemicals and also a well ventilated area.

Second warning:  Always always always mix acid to h2o2, never the reverse -
I can't explain why this is important, I am not a chemist, but it has to do
with the way the acid will mix with the water, along with splashing and so
forth.

Second warning: Storage - this stuff is a pain in the arse to store.  Once
the seal is broken on the bottle, fumes can escape and start to corode
nearby metal (yes, the fumes from this stuff can easily destroy metal) - I
currently use an outbuilding away from the house to store the excess that I
haven't mixed up.  The mixed up batch I neutralized after my experiment and
disposed of.  Neutralizing was simply adding an alkaline to it (I used
baking soda, I've read other sites that recommend a watered down amonia
recipe as well - but  I'd recommend searching for neutralizing muriatic acid
on the net before attempting)

Well, having used muriatic acid in the past (when I was younger, I used to
be the one to take care of our pool, and it was commonly used as a pool
chemical to change pH levels) I figured this was something I was willing to
try.

The mixture on the site I had read was 50% H2O2 to 50% muriatic acid.  THIS
MIX IS TOO STRONG.  I mixed at ~33% acid to 67% h2o2 and it was still strong
enough to etch a 4.5x7 board of mostly copper (it was an experiment board
that I had tried on a CNC, so although the board was unuseable, not much
copper was missing) - it etched this thing in <1.5 minutes, I'd say closer
to about 40 or 50 seconds, and this was with very light agitation (mostly
just grabbing the string I had tied around the board and shifting it a
little bit).

It dissolved the copper incredibly fast, and didn't harm anything under the
little etch resist writing I had put on the board.

Final thoughts:  Muriatic acid makes a great etchant BUT - it is extremely
dangerous to utilize, and must be utilized in a WELL ventillated area or
outside only.  indoor use without sufficient ventilation can be extremely
hazardus.  I think a much weaker mix with a longer etch time is desireable,
I'd rather do a 1 to 4 or perhaps a 1 to 5 mix (I may experiment with levels
used to acid wash clean concrete which is 1 to 10) - longer etch with more
safety appeals to me.

I'm also thinking that some of the other concrete cleaning acids may work
well (the ones that are weaker then muriatic acid) with less risk to ones
self.

Also - you need to utilize h2o2, otherwise there will be no good reaction
(something about the extra oxygen molecule that makes the process work) and
it will eat thru the copper, but it will take a very long time.

These are my thoughts and feelings and felt I should share.  as I said
before I'm sure many know about this little trick, some probably use it.  If
you choose to utilize this method of etching you do so AT YOUR OWN RISK - I
will assume no responsibility if you hurt or kill yourself.  I strongly urge
you to search the net on muriatic acid pcb etching to see how others have
done it.

-Tony

Cupric chloride etching?.I think the ratio should have been more like
muratic  12% volume to water, and a teaspoon of h2o2 just to get it started.
Toss in some copper, aka pcb, and you get the cycle started. It will never
need fully replacing is properly maintained. IMO next to cnc etching, this
is the best, most environmentally friendly and cost efficient  method.

Search this group and read all about it.
50 / 50 mix was way way dangerously wrong!

JT

----- Original Message ----- 
From: "Tony Harris" <tony@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, January 16, 2004 6:24 PM
Subject: [Homebrew_PCBs] Etching - thoughts and a respect for chemicals.


> Hi all,
>
> I know that I don't post much to this list and act mostly as a lurker, but
I
> recently tried something that I found on a website (that I am sure many,
if
> not most on this list have already come across).  This will probably end
up
> a fairly long email, and for that I kind of apologize, but for those that
> don't know or never realized, it might be good.
>
> We all know that etching is evil necessity if we wish to make our own
> boards - even though many of us utilize mechanical etching via CNC, some
> circuit densities don't make that possible unless you have a major high
> dollar machine (which of course most of us can't afford).
>
> Well, I, like many others, don't have easy access to etching chemicals -
> either we pray that radio shack happens to have a bottle of the nasty
stuff,
> or we order from a supplier.
>
> I came across a website that mentioned using a muriatic acid and hydrogen
> peroxide mix to etch boards.  This interested me as it would greatly
reduce
> the cost of a batch of etchant, and would be much easier to obtain
> (considering you can get muriatic acid at local hardware stores.
>
> First a warning:  This stuff is major dangerous.  if you think ferric
> chloride is bad, this stuff makes ferric chloride practically look like
> water.  Do not attempt to use this stuff if you don't have a very healthy
> respect for chemicals and also a well ventilated area.
>
> Second warning:  Always always always mix acid to h2o2, never the
reverse -
> I can't explain why this is important, I am not a chemist, but it has to
do
> with the way the acid will mix with the water, along with splashing and so
> forth.
>
> Second warning: Storage - this stuff is a pain in the arse to store.  Once
> the seal is broken on the bottle, fumes can escape and start to corode
> nearby metal (yes, the fumes from this stuff can easily destroy metal) - I
> currently use an outbuilding away from the house to store the excess that
I
> haven't mixed up.  The mixed up batch I neutralized after my experiment
and
> disposed of.  Neutralizing was simply adding an alkaline to it (I used
> baking soda, I've read other sites that recommend a watered down amonia
> recipe as well - but  I'd recommend searching for neutralizing muriatic
acid
> on the net before attempting)
>
> Well, having used muriatic acid in the past (when I was younger, I used to
> be the one to take care of our pool, and it was commonly used as a pool
> chemical to change pH levels) I figured this was something I was willing
to
> try.
>
> The mixture on the site I had read was 50% H2O2 to 50% muriatic acid.
THIS
> MIX IS TOO STRONG.  I mixed at ~33% acid to 67% h2o2 and it was still
strong
> enough to etch a 4.5x7 board of mostly copper (it was an experiment board
> that I had tried on a CNC, so although the board was unuseable, not much
> copper was missing) - it etched this thing in <1.5 minutes, I'd say closer
> to about 40 or 50 seconds, and this was with very light agitation (mostly
> just grabbing the string I had tied around the board and shifting it a
> little bit).
>
> It dissolved the copper incredibly fast, and didn't harm anything under
the
> little etch resist writing I had put on the board.
>
> Final thoughts:  Muriatic acid makes a great etchant BUT - it is extremely
> dangerous to utilize, and must be utilized in a WELL ventillated area or
> outside only.  indoor use without sufficient ventilation can be extremely
> hazardus.  I think a much weaker mix with a longer etch time is
desireable,
> I'd rather do a 1 to 4 or perhaps a 1 to 5 mix (I may experiment with
levels
> used to acid wash clean concrete which is 1 to 10) - longer etch with more
> safety appeals to me.
>
> I'm also thinking that some of the other concrete cleaning acids may work
> well (the ones that are weaker then muriatic acid) with less risk to ones
> self.
>
> Also - you need to utilize h2o2, otherwise there will be no good reaction
> (something about the extra oxygen molecule that makes the process work)
and
> it will eat thru the copper, but it will take a very long time.
>
> These are my thoughts and feelings and felt I should share.  as I said
> before I'm sure many know about this little trick, some probably use it.
If
> you choose to utilize this method of etching you do so AT YOUR OWN RISK -
I
> will assume no responsibility if you hurt or kill yourself.  I strongly
urge

> you to search the net on muriatic acid pcb etching to see how others have
> done it.
>
> -Tony
>
>
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs
>
> Yahoo! Groups Links
>
> To visit your group on the web, go to:
>  http://groups.yahoo.com/group/Homebrew_PCBs/
>
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>
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>  http://docs.yahoo.com/info/terms/
>
>

-trim-

> you to search the net on muriatic acid pcb etching to see how 
others have
> done it.
> 
> -Tony

Tony, 
Your ratio is WAY off. There was a recent thread on this and I 
suggest you look over the archives of the past couple (3) weeks.

The basic jist is 15% Muratic (hydrochloric) acid and about 2% H2O2. 
This isn't the acid etching, it's Cupric Chloride. The free oxygen in 
the H2O2 breaks the hydrogen from the hydro-chloric acid, producing 
water and free chlorine. The free chlorine recombines with copper 
from the board and produces copper-chloride. There's more to it, but 
I'm not going to reprint it here. There's a lot of great technical 
details on previous posts and in the links section. Do note though 
that acid from the hardware store is about 30% to start with and 
various H2O2 supplies are different percentages too.

Others reccomend against medical 3% H2O2, saying that it's not strong 
enough. I'm using it successfully. I've a solution of 1 part 32% 
acid, and 2 parts 3% medical H2O2 and it works fine. Stronger H2O2 
can be used to recharge the etchant, but you can also recharge it by 
bubbling air through it. THERE IS NO NEED TO EVER DISPOSE OF ETCHANT 
AGAIN. It can be rejuvinated endlessly. Again, read about it in the 
links section.

-Denny

Hi Denny,

As I had mentioned in my post a 50-50 mix was IMHO way too strong, and I had
realized that while I was combining - at this point I was still in a big
guessing game (I only wish I were a chemist sometimes, would have made some
of this make much more sense and I probably would have known the info
presented to me was off, and that even my 33/67 was off)....

<snip>
The mixture on the site I had read was 50% H2O2 to 50% muriatic acid.  THIS
MIX IS TOO STRONG.  I mixed at ~33% acid to 67% h2o2 and it was still strong
enough to etch a 4.5x7 board of mostly copper
</snip>

I also mentioned that I felt a smaller ratio would work just as well...

<snip>
I think a much weaker mix with a longer etch time is desireable,
I'd rather do a 1 to 4 or perhaps a 1 to 5 mix
</snip>

1 to 5 is a 20% ratio of acid to the remaining components of the mix - so
that isn't too far off from 15%.  I'm glad to hear about the even lower then
I figured mixture ratio.

I do see why I didn't find anything - I spell the acid Muriatic - which is
the only way I have ever known how to spell it (see msds:
http://www.aldenleeds.com/html/muriatic.html) - I now see that it can be
spelled differently by people (muratic) - searching thru the emails with
muratic as a spelling would have given the results you spoke of.

I honestly didn't know it combined to do cupric chloride etching - Thank you
for that extra piece of info, I wish I had known about it before, I could
have forgone some of the bad mixture ratio sites, and a search on cupric
chloride etching would have resulted in a lot more accurate info I believe
(plus, I wouldn't have posted a long note on something that had just been
gone over recently, oh well, my bad).

Also the previous sites I had read this on had talked about just a mixture
of the acid with h2o2, now that I've been able to read a bit more from some
of the links, as well as the now found previous discussion I understand more
and find myself with a ton of extra h2o2 rofl.

-Tony

> The basic jist is 15% Muratic (hydrochloric) acid and about 2% H2O2.
> This isn't the acid etching, it's Cupric Chloride. The free oxygen in
> the H2O2 breaks the hydrogen from the hydro-chloric acid, producing
> water and free chlorine. The free chlorine recombines with copper
> from the board and produces copper-chloride. There's more to it, but
> I'm not going to reprint it here. There's a lot of great technical
> details on previous posts and in the links section. Do note though
> that acid from the hardware store is about 30% to start with and
> various H2O2 supplies are different percentages too.
>
>
> -Denny

well, i use the method myself, and as it was already written
it is not dangerous at all if you take care.

I store the bottle of HCL and the bottle of H2O2 (bot 35% 1 liter plastic)
in the same room where my tools are. No corrosion problems.
the ONLY problem i ever had was forgetting a jar filled with some etchant.
This vaporized and when i came back a lot of drills and other nearby tools 
were
corroded.

The used Etchant i stored, also for years, in a glass bottle with a lid 
which has a 1mm hole in the top.
(because i wanted to release the h2o2 pressure).
My new etching jar will only be a tupperware container and the lid of this 
is also enough to prevent
any corrosion.


You see, no problems at all with the stuff on this site...
The bottles i use are the "standard" from my chemists shop,
Poly Ethylene with a red "child safe" cap (the one you need to press
down to unscrew). the cap has such a soft, "foam plastic" seal in it.
They are absolutely airtight.

Only the HCl Bottle shows salt on the outside, which seems to come through 
the
PE. it is not much and i have placed it in a sleeve of another bottle
(only because i don't want to touch this salt every time).



I add the H2O2 to the etchant (which seems to be the easiest way)
and never have seen any splashing at all.


If you use the correct concentrations this is a very kind and forgiving 
etchant,
and very cheap. I think it will work out for you if you use the right 
concentration.


Wear safety googles all the time, old clothing and gloves are suggested.


ST

> I do see why I didn't find anything - I spell the acid Muriatic - 
which is
> the only way I have ever known how to spell it (see msds:
> http://www.aldenleeds.com/html/muriatic.html) - I now see that it 
can be
> spelled differently by people (muratic) - searching thru the emails 
with
> muratic as a spelling would have given the results you spoke of.



Oh how we lament the poor spelling.

If you google muriatic, you will get 22,900 hits, 
google muratic (without the 'i' ) and you get 2,460 hits and it also 
offers the correct spelling.

I often will change the subject line when the topic shifts, 
especially when the thread gets a little long.

That would be a hint to all you who might ever search the archives.  
This list is much better than most for NOT posting  'newest newbie 
question' that then has 30 replies.

A word on chemical storage...

Whatever bottle you use, it would be wise to get a container, like a 
tupperware bucket that is of greater volume than your container and 
place your container in that bucket.  

That does a few things.
One, it adds a level of protection from bumping.
Another it adds a space around the container for atmospheric 
reactions and a place to catch those.
It also adds a layer of containment if two chemicals were to break 
and it prevent them from mixing.

Also, make sure the secondary containment vessel is compatible with 
the chemical which it will hold.

Also, one can place some substance in the bottom of the containment 
vessel that will neutralize the acid or base in the event of a leak.


Anybody wanna offer what is compatible with the chemicals in this 
thread ?  That would put more data into a single place to find it for 
a future search.


Muriatic acid, aka HCL, aka hydrochloric acid ?


H2O2, aka, Hydrogen peroxide?


Cupric chloride ?



Dave

>
> Muriatic acid, aka HCL, aka hydrochloric acid ?
>
>
> H2O2, aka, Hydrogen peroxide?
>
>
> Cupric chloride ?
>
>
>
> Dave
>
>

As said my bottles are made of PolyEthylene.
It is white/transparent (you can see how much is in it).

HCl seems to come through slightly (salt crystals on the outside.)
Do you know which salt this may be?
I put a second bottle around it, only to prevent the salt getting on my 
fingers.

I bought the HCl in this bottle, so i think the manufacturer knows what he 
does.


It is the same with the etchant. if i remember correct i had it in a 
plastic (PE) bottle
before and the salts did form on the outside. then i put it in a 
thinkwalled coca cola glass bottle
(1l vintage special edition i think - these bottles are not normally sold)
and there is no salt on the outside to be found.


There is some rule, is it "acid in plasic, base in glass" or is it the 
opposite?


In the links section you will find the chemical comptibility page....
But it obviously can't tell which salt is on the outside of the HCl bottle.
I would like to know which salt this is.

ST