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
>
>
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