Homebrew PCBs

Can you describe more of what you are seeing ?
Is the copper changing appearance ? Copper that has been rubbed down with a 
mild abrasive like Scotch Brite looks more like a reddish copper color with 
fine scratches visible on the surface. When immersed in the etchant the 
copper should turn pink color in the first 10~30 seconds (due to 
microscopic roughening) and after a minute the fine surface scratches 
should disappear. Are you seeing this ? If not then I suspect you don't 
have ammonium persulfate or your copper is heavily contaminated on the 
surface thus protecting it from the etchant. Surface residue is common with 
negative dryfilm photoresists that have been on the copper for a long time 
(>6 months).

Your too strong, as other has said the normal makeup of (NH4)2S2O8 is 
approximately 200 g/L.

Adam

mumin55555 wrote:
> i tried for the first time to use ammonium persulphate instead of 
> ferric chloride. i built a nice etcing tank with a heater at about 
> 50 degree celcius and an air pump. i used about 1kg of ammonium 
> persulphate with 2 litre of water (at the first place i used much 
> less ammonium persulphate, but when i saw nothing is happening i put 
> more).
> help!!!!!!!!!!!!! i need it very urgent!
> thanks a lot,
> mumin.
> 
> 
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