Hi all. I'm trying to solve a problem of pitting around the holes after ammoniacal etching. I suspect my problem is insufficient deposits of electroplated tin resist around the holes, which is making it more susceptible to attack by the etchant. The reason I think its a tin problem is because prior to etching, the tin deposits appear solid and smooth when viewed under a microscope. However after etching there is evidence of pitting around many holes. The problem seems to go away with excessive plating, about 8um or more. Normally I've not had a problem at only 2~3um. Also is it normal to have a small amount of white foaming hydrogen gas above the PCB while tin plating ? The tin bath is an acid stannous sulfate type with brighteners, and has always been a milky yellow appearance. Adam Seychell --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 -----------------------------------------------------