Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan 
<stefan_trethan@g...> wrote:
> On Tue, 18 May 2004 10:40:31 -0000, onenastyviper 
> <oneNastyViper@h...> wrote:
> 
> > Maplins has the hexahydrate, I thought there was two types:
> > hexahydrate and another anhydrous one?
> > Don't ask me if there is a difference, I haven't studied any 
chemistry
> > but on a website its said to use the hexahydrate not the anhydrous
> > one???
> > This etching chemistry is complicated...all I want to do is etch
> > small circuits in a little tub with the least amount of hassle 
with
> > easy availble and reasonably safe chemicals (ie I don't want to 
wipe
> > out a little part of swinton:-P)
> >
> > PK
> 
> 
> The chemistry is not really complicated, if you want to maintain a 
good 
> etchant
> with least cost and no waste it is complicated.
> If you only want to make the occassional pcb and don't care if you 
put in
> 5cent or 10cent worth of chemicals then you need not regard the 
chemistry 
> much.
> 
> I still suggest using CuCl.
> A simple and effective etching tank is a tupperware container.
> The flat ones work just fine, the PCB need not be vertical and you 
need
> much less etchant than in e.g. a cerial container.
> The lid is tight enough to prevent vapor escaping, and also 
prevents a 
> disaster
> if you knock the tank over while in storage.
> For single-sided pcbs a piece of tape makes a great pcb handle.
> For CuCl you only need HCl (Muriatic acid), and H2O2, which is both 
easy 
> to get
> hold of.
> 
> The procedure when etching is to place the board in the ethant and 
add a 
> small
> amount of H2O2. Then it etches, you take the board out, put the 
etchant 
> away,
> and reuse next time again only adding a small amount of H2O2.
> 
> If one day the etching stops and you see blue sludge on the copper 
the HCl 
> is spent.
> add a bit and on it goes again.
> 
> That is all the chemistry involved for the occassional PCB.
> 
> ST


I'm no chemist, but HCL is hydrogen and Clorene ?
H2O2 is hydrogen and oxygen.

add Sodium bi-carbonate (ie: Baking Soda, not baking powder) to the 
mix and you bind the oxygen to the carbon and get CO2 and that is 
harmless in small quantities

The CL is bound to the  sodium so you get NaCL or salt and that is 
harmlelss in small quantities.

So... for the end of life thing you wind up with copper as the big 
problem.  

Once neutrlaized, the above mix can be dried without releasing any 
air born toxins and leave you with the dried powders.

Those you can probably reduce to some very small size provided you 
didn't just dump a box of baking soda into the bowl.

Then put at in a plastic bag and and mark 

NaHCO3  - baking soda
NaCL-  from HCL and NaHCO3 reaction
Cu - copper


and drop off at your local hazardous waste facility.


Is my chemistry correct ?


Would electrolysos in a container with a box of baking soda on top be 
anohter way to reduce the hazards ?

Dave