I believe the chemical term is "peroxide". There are two formulations in common use, one is based of persulfate (which is the one you suggest) and the other is based on hydrochloric acid. I suggest that those who are interested visit: [email protected]

Myself, I use the old, reliable ferric chloride method. I don't know that it has any advantages, except stabliity. The peroxide solutions need to be replinished or made fresh much more frequently. Ferric chloride will sit for years and still be active. It has several disadvantages, including that you cannot see the progress of the etching; whereas, the peroxide-based etchants are relatively clear. However, removing the PCB to check the etching is not really a big problem on a small scale. John