Ed: We have always used anhydrous ammonia, liquid ammonia resulted in sludge out problems. It is introduced to the bottom of the etch sump thru a multi-leg gas sparge and controlled with a pH probe. A sp.gr.controller is used to add the replenisher. The key was making sure things stayed clean and not plugged or crusted over. You can reduce the ammonia losses when not operating by closing down the vents. I would recommend you talk with your ethcant supplier's technical engineering folks. They should be able to supply you with additional information on design and equipment. Regards Michael Barmuta Staff Engineer Fluke Corp. Everett WA 425-446-6076 -----Original Message----- From: May William D (Dean) CNIN [mailto:[log in to unmask]] Sent: Monday, May 19, 2003 7:56 AM To: [log in to unmask] Subject: [TN] Controlling pH of ammonia etcher Due to the start/stop nature of our pcb shop I am looking to control the pH of an ammoniacal copper etcher using aqueous ammonia. After the etcher has not been used for a couple of days to a week the pH has dropped somewhat. I would use a metering pump to add the ammonia to the sump of the etcher. Are there any concerns I should be aware of before setting the aqua ammonia up? What grade of ammonia must I use so that I don't contaminate the etchant? Can you add ammonia too fast to cause a problem? Can you add too much over time? Are there other ways to accomplish the goal? Is there a proper way to introduce anhydrous ammonia so that the solution can properly metabolize the anhydrous into the solution? It seems to me that contact time with the anhydrous would need to be considered for it to do any good? Thanks for your consideration! Edward A. McAtee Crane Division, Naval Surface Warfare Center (NSWC Crane) Harnessing the Power of Technology for the Warfighter Code 6086, Bldg. 38 300 Highway 361 Crane, IN 47522-5001 Ph: 812.854.3892 Fax: 812.854.1174 Email: [log in to unmask] --------------------------------------------------- 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 -----------------------------------------------------