Homebrew PCBs

Stefan Trethan wrote:
> hmm two questions arised now:
> 
> first i have to inform myself about stabilizers and how long they may be useful to conserve the H2O2. i 
> don't assume they would help if there is one week between the prototypes.

Stefan, you might be interested reading articles on 
http://www.h2o2.com/ :)

> 
> 
> the second issue is regenerating the fluid with air oxygen, i'm really wondering if this would also work 
> with this etchant.
> when using hydrocloric it converts Cu2Cl2 to CuCl2 and the CuCl2 does thake the copper off the pcb and 
> gets Cu2Cl2 (as i have understand it). but in your bath CuSo4 builds.. have no idea how this all works 
> together and if your solution may be regenerated with air oxygen.. my chemistry knoweledge is bad..

 From what I've read the reaction of copper with sulfuric 
acid / hydrogen peroxide does not require air. The overall 
reaction is
Cu + H2O2 + H2SO4 -> CuSO4 + 2H2O

I don't have any experience with this etching, so but I 
don't think its fast as (CuCl2+HCl) or FeCl3 etching. I 
believe its used commercially for 'microetching' and etching 
with solder plating resists, just as Tom (twb8899) explained.

I've been playing around with a type of etching solution 
that theoretically just consumes water and air. I copied it 
from an old patent, and is based on the widely used 
ammonical chloride enchants. It replaces the ammonia with 
monoethanolamine (MEA), so it doesn't smell, or evaporate 
gas. I got 1 liter of MEA form an place that prepares 
industrial cleaning chemicals. Its used in some detergents.

approximate concentrations of the solution I made up is.
100g/l ammonium chloride
200g/l cupric chloride
200g/l MEA
pH 7 to 8

I'm guessing the overall reaction is
	
Cu + O + H2O -> Cu(OH)2

Note:, the copper in solution is always at saturation, so 
the Cu(OH)2 produced falls out as a sludge.

Yes, I confirmed it worked by etching a relatively large 
chunk of copper in just 100 ml of solution and although it 
took a week, it etched away, creating a lot of copper(II) 
hydroxide sludge. I drained off the solution into another 
container and bubbled air through it for about a day. Then 
it etched a tiny piece of 1/2 oz PCB in about 30 minutes at 
room temperature. The sludge is messy and it could prove 
difficult to separate efficiently, so I wouldn't recommend 
it as a hobby etchant. I'm guessing this is also the reason 
its not used commercially.

Adam