I was looking for a rough estimate. We were starting with fresh ferric
chloride for each 3" x 4" board and now see that it was not necessary. Maybe
a better question is - is there a simple test to know when the ferric
chloride is spent? Maybe put a single, very fine copper wire in the solution
and time how long it takes to vanish?
Thanks,
Rick
-----Original Message-----
From:
Homebrew_PCBs@yahoogroups.com [mailto:
Homebrew_PCBs@yahoogroups.com]
On Behalf Of smilingcat90254
Sent: Thursday, November 22, 2012 7:51 PM
To:
Homebrew_PCBs@yahoogroups.comSubject: [Homebrew_PCBs] Re: Ratio of Ferric Chloride to copper?
hmmm... can't really go by volume of FeCl3 (Ferric chloride) and volume of
copper. Wht you need to know is how many moles of each (chemists way of
counting number of atoms or molecules) will react together. read about
atomic weight, Copper weighs 29gram/mole whereas FeCl3 weighs 77g/mole.
And now you want to know how much ferric chloride can "eat" copper.
It takes two molecules of ferric chloride to "eat" one atom of copper and
turn it into one molecule of Copper chloride (CuCl2). I think it was...
So you need 154g of ferric chloride to etch 29g of copper.
You have to know the concentration of your ferric chloride solution.
BTW, ferric chloride isn't an acid, its a salt like sodium chloride (table
salt).
hope this answers your question.
--- In Homebrew_PCBs@yahoogroups.com, "RickS" <rgsparber@...> wrote:
>
> Does anyone know the ratio of needed Ferric Chloride by volume to the
volume of copper being removed? I am assuming 110F for the acid and constant
agitation.
>
> Thanks in advance,
>
> Rick Sparber