Homebrew PCBs

On 20/03/12 07:39, Philip Pemberton wrote:
> On 19/03/12 08:00, Russell Shaw wrote:
>> On 19/03/12 12:18, Leon Heller wrote:
>>> If it's dark green, it's probably exhausted.
>>
>> If it's dark green, it will etch perfectly well using a different chemistry if
>> you use bubble agitation, and add a bit of hydrochloric acid from the hardware
>> shop every few weeks.
>>
>> I get full etch in 10-15mins at room temperature like that.
>
> Well, I've just filtered the etchant through a piece of kitchen roll (my
> first choice was coffee filter paper -- I didn't have any, so I figured
> kitchen roll would work as an alternate).
>
> I ended up with a green liquid, and brown paper...
>
> So I think it's a fair bet there's some kind of copper salt in the
> solution, along with a tiny bit of iron (it's got a yellowish tint to it).
>
> I've thrown in 200ml of brick cleaner (10% HCl, ~\ufffd10 for five litres
> from B&Q) and set the valve on the air pump to full. Right now I have
> foamy green etchant... I'm going to leave it for an hour or so and see
> what happens when I throw some FR4 board offcuts in (lord knows I have
> plenty of those after last night's complete abortion of a PCB etching
> attempt).
>
> This should be interesting...

I would have added the HCl, but also left the solids in there to dissolve. You 
may have removed the active ingredients;)