Re: A different Etchtant (was Re: Homebrew PCB mailing listinvitation)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "R Heidlebaugh by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rheidlebaugh-at-zialink-dot-com>

on 12/11/01 5:40 PM, Tesla list at tesla-at-pupman-dot-com wrote:

> Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <m.j.watts-at-massey.ac.nz>
> 
> HI Steve,
> The reason I asked was so that I wouldn't be duplicating
> otherwise available information. From the two replies I've received,
> it seems that the mixture I use is not widely known, so here it is.
> 
> The basic mix: 1 part commercial grade hydrogen peroxide (about 30% I
> think), 1 part fuming hydrochloric acid, AND 6 - 8 parts water with
> the H2O2 and Hcl separately added *slowly* to the water. This
> concentration gives a useful etching speed. Waste products are copper
> II chloride (soluble with a low pH) and water.
> 
> DO's:
> - Ventilation when pouring the Hcl out of the bottle
> - A *good* impervious resist with no pinholes
> - Occasional agitation to release small bubbles from the surface of
> the board
> - water at hand to wash yourself if you get acid or peroxide on your
> hands. The peroxide in particular will attack skin very rapidly
> and you'll feel it.
> 
> DON'Ts:
> - *DO NOT* mix the undiluted acid and peroxide together. The
> mix will produce copious amounts of chlorine (none will be
> produced if the mixing directions above are followed).
> - be tempted to use a strong mix to make etching much faster.
> A strong mix will not only etch a board bare in a matter of
> seconds, it will boil as well (spatter factor).
> - be tempted to top up the acid and/or peroxide if the etching
> crawls to dead slow. Make a fresh mix instead.
> 
> Too much acid gives the mix a green hue during etching and too much
> peroxide makes the copper appear shiny. Ideal is for an oystery sheen
> to cover the copper if the board is lifted out of the mix and
> drained. If the acid is becoming exhausted, insoluble blue deposits
> appear on the copper. A correct mix will give the mixture a blue
> colour, deepening as more copper is dissolved.
> 
> The basic action seems to be that the peroxide oxidizes the
> copper leaving the oxide easy for the acid to deal with.
> 
> Finally, the waste salt can be usefully mixed with sodium carbonate
> (washing soda) or sodium bicarbonate (baking soda) to make a useful
> anti-fungal spray for fruit trees. The result is copper carbonate
> (low solubility) which needs to be washed several times to remove the
> soluble NaCl.
> 
> I started using this recipe about 30 years ago and it is a
> winner. No more awful stains or waiting for hours. I can't claim
> originality for it - I first saw it mentioned in a letter in an
> electronics periodical "Practical Electronics".
> 
> Regards,
> Malcolm
> 
> On 11 Dec 2001, at 12:33, Tesla list wrote:
> 
>> Original poster: "Steve Greenfield by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <alienrelics-at-yahoo-dot-com>
>> 
>> I don't know, you should join and ask. ;')
>> 
>> http://groups.yahoo-dot-com/group/Homebrew_PCBs/
>> 
>> I've used whatever Radio Shack sells and found at best
>> it is adequate, at worst a waste of money and time.
>> I've also used some dry stuff I think was Ammonium
>> Persulfate that I was satisfied with.
>> 
>> A colleague told me he's used a weak Nitric Acid mix
>> to etch boards -very- quickly but you have to be well
>> rested, have a lot of ventilation and really be paying
>> attention. And your etch resist coating had better be
>> complete.
>> 
>> Steve Greenfield
>> 
>> --- Tesla list <tesla-at-pupman-dot-com> wrote:
>>> Original poster: "Malcolm Watts by way of Terry
>>> Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>
>>> 
>>> Hi Steve,
>>> What etching fluids are used by your
>>> group members?
>>> 
>>> Regards,
>>> Malcolm
>>> 
>>> On 6 Dec 2001, at 8:03, Tesla list wrote:
>>> 
>>>> Original poster: "Steve Greenfield by way of Terry
>>> Fritz
>>> <twftesla-at-qwest-dot-net>" <alienrelics-at-yahoo-dot-com>
>>>> 
>>>> I've started a Yahoo Group on making, etching,
>>>> soldering printed circuit boards yourself.
>> 
>> 
>> 
>> 
> 
> 
> 
> 
I will have to try your mix. It looks like a less messy mix than Ferric
chloride. Ferric chloride has one redeaming virtue. It's cheep. I get liquid
mix from the same truck that delivers to the sanitary waste site . I have to
be there on delivery day with a wide mouth 10 gal container to collect.
  Robert  H