Adam, Again, from about 30 years ago I looked at the same thing. Clyde Coombs Printed Circuit Handbook was very helpful in understanding this. I wound up with a peroxide regen and had the lab look at it by titrating with peroxide until the brown color went away. The calculation I gave them for the tank addition was 85% of what was needed to avoid an overaddition and too much activity. George -----Original Message----- From: Adam Seychell [mailto:[log in to unmask]] Sent: Wednesday, April 09, 2003 5:00 AM To: [log in to unmask] Subject: Re: [TN] cupric chloride parameters Phil, You response tells me I am more or less on track with the chemistry. It amazes me the fact that free acid concentration can vary across such high range. It wouldn't be surprising then to hear conflicting arguments on what is the best level of acid to use in CuCl2 etching. What I hope to achieve is a 5 gallon immersion etching tank, for occasional etching of single sided prototype PCB's. What you describe about the slow regeneration with air bubbles is spot on to my observations. Yes, the regeneration rate via air bubbles alone is many times slower than the rate of copper being dissolved. Fortunately the tank will have limited use and so it may continue being regenerated for a long time (e.g several hours) after the PCB has finished etching. I believe the volume of solution should be sufficient to hold the limited amount of copper(I) produced during the relativly short etching period. To test when regeneration is complete, I take a few drops of etchant and add to 5 ml of water, if a cloudy precipitate forms then it indicates a significant amount of copper(I) is present and regeneration must continue. I have tested this on small scale, and it seems to give a good indiation, the time for regeneration can be up to 3 or 4 hours. I guess the industry have much cleaver more automated methods of keeping the solution regenerated with chemical oxidizers. Adam --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------