That’s funny, most people were wondering why Monday afternoon was so far from Friday looking forwards and such a short time ago looking back........and the balance of the group was wondering whether they could get away from their desks to catch the end of happy hour................8-) I am sure the group will give you a serious answer, I am just working up for Friday...........8- ) John -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Adam Seychell Sent: Monday, June 12, 2006 4:03 PM To: [log in to unmask] Subject: [TN] cuprous ions in ammoniacal chloride etching I am wondering if there is a simple test for cuprous ions in ammoniacal chloride alkaline etching, and thus determine when to increases or decrease the air ventilation intake of the etching machine. I am brewing my own chemistry based on typical operating parameters of ammoniacal chloride etchants. Copper 2 ~ 2.5 Molar Chloride 4.5 ~ 5 Molar pH 8.0 ~ 8.6 Temp. 40 ~ 45 °C I discovered just like with acid cupric chloride etching, that when the cuprous content reaches to even small concentrations then the etch rate is severely affected. In the lab, I tested as little as 5g/L of dissolved copper in the cuprous state will slow etch rate, and at 10 g/L it becomes virtually a stand still. For acid copper chloride etchants, the loss of its bright green color is a quick indicator of cuprous ions being present, and even 0.5 g/L will show beginnings of color change. However in alkaline etching the cuprous ions do not appear visible or change the solution color. I have heard about ORP (oxidation-reduction potential) probes used in acid cupric chloride machines. Can these same probes be used in ammoniacal chloride etchants ? My chemistry is a bit poor, although I'm wondering if is possible to make such a probe, using a standard reference electrode (e.g Ag/AgCl ) and a piece of copper wire as the indicator electrode. Adam Seychell --------------------------------------------------- Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------