Homebrew PCBs

You can put more copper oxide to increase etch rate. From memory 
I think its around 140 g/L of copper(II) ions is good concentration.
What copper oxide did you get, the black stuff or red ?
Black is more common which is copper(II) oxide.
100 g copper(II) oxide (black) = 66g copper
100 g copper(I) oxide (red) = 89g copper




Les Newell wrote:

> My chemicals finally arrived today so I made up a batch of cupric 
> chloride etchant. The ingredients I used were:
> 
> 250g copper oxide
> 790 ml 35% hydrochloric acid. This is probably not as accurate as going 
> by weight but there is no way I am letting that stuff near the kitchen 
> scales :-)
> enough water to make up 2.5 litres
> 
> I added the acid to about 1 litre of water a little at a time, stirring 
> all the time. Once all the acid was in the solution reached 30 deg 
> centigrade, from 13 deg C when I started. I then added the copper oxide 
> and stirred well. I dumped the whole lot into a 2.5 litre container and 
> topped it up with water.
> 
> The end result was a fairly deep green solution. In my etch tank at 35 
> deg C it took 20 minutes to etch a board which seems slightly slower 
> than new ferric but a lot quicker then the manky old ferric I was using 
> :-) It does not seem to be as agressive as ferric. The board I used was 
> an old board that was over exposed and has been lying around for about a 
> year. Some areas took a while to start etching due to accumulated 
> oxides, fingerprints etc. A piece of the same board dunked in ferric 
> seemed to etch more evenly.
> 
> 35% HCl is pretty nasty stuff. I mixed up the solution outdoors in 
> fairly damp conditions and there were clouds of fumes coming from the 
> container of acid.
> 
> All I need to do is get the new light box sorted out and I will be able 
> to try the etchant properly.
> 
> Les
> 
> 
> 
> 
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