johnh@macadam.mqcs.mq.oz.au (John Haddy) (03/18/91)
>I have also used ammonium persulfate (with a mercury chloride catalyst) >as an etch. It's only advantage is you can tell how "used" the solution >is as it turns blue from the dissolved copper sulfate. The stuff is very >poisonous (due to the catalyst) and should probably be avoided. > Due to concerns here regarding our use of mercury chloride, we queried one of the academics in the chemistry department. He replied with a list of other suitable additives to our ammonium chloride - the most suitable of which was to add a small quantity of phosphoric acid to the etch bath. Since we already use this acid as a flux for some of the more "difficult" metals (steel, Nichrome etc.), we had no problems purloining some for the etchant tank. It's worth noting that ammonium persulphate needs to be heated in order for it to work effectively as an etchant - another good reason to avoid mercuric compounds (fumes etc.). John Haddy johnh@zubrette.mqcs.mq.oz.au until the new domain names start working! :-) -------------------------------------------------------------------------------- | johnh@mpce.mq.edu.au # School of Mathematics, Physics, | | # Computing & Electronics | | John Haddy ph 61-2 805 8959 # Macquarie University NSW 2109 | | fax 61-2 805 8983 # AUSTRALIA | | =======================================| | Electronics Technical Services Group <=TDM=> High Speed Networks Group | --------------------------------------------------------------------------------