On Sun, 05 Feb 2006 15:32:31 GMT, Lew Hartswick
wrote:


Yes, It was an intresting "view", the room where the company I worked
at in the early 1950s started to do printed circuits using feric
chloride as the etchant. What a mess. :-)
...lew...

I've seen several PCB websites that have recently been mentioning that
muriatic (hydrochloric) acid dissolved 50% with water, then mixed with
high strength hydrogen peroxide (40 volume or higher - about 15% or
more) can be used to etch circuit boards and brass. While this
apparently does work, I'm curious as to just what kind of substance it
creates. I would have thought that HCl + H2O2 + H2O would produce a
neutral chemical from the mixture of a strong acid and strong base. I
regenerate the ferric chloride that I use for brass parts etching with
hydrogen peroxide and acid, but this simply recombines the spent
chemical (FeCl2) back to FeCl3 - the iron is an important ingredient.
The ones that reccomend to mix acid with peroxide also mention that
it's still acidic and will burn your skin, wheras ferric chloride,
while ungodly messy, won't normally burn skin quickly. (My setup is
such that I never have to touch the chemical to put the parts in or
check the progress. I use gloves to take them out, and if it splashes
I simply use a rag soaked in baking soda + water to wipe it off).

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