Steven - I had to look a bit in some old files to see the formal reference between "thin immersion silver" and "thick immersion silver". The first IPC 4553 standard, dating to 2002-2004, did make a formal difference between those. However, by the time of the 4553A revision, around 2008 or 2009, the formal difference was discarded. The allowed thickness included the range formerly covered by "thin" and "thick". While I only know a limited amount about the "chemistries", my impression is that today there is no chemistry for thin and for thick. Bob Lazzara has previously pointed out that dwell time and temperature can change the immersion silver thickness. Denny Fritz -----Original Message----- From: Steven Kelly <[log in to unmask]> To: TechNet <[log in to unmask]> Sent: Mon, Aug 10, 2015 3:47 pm Subject: [TN] immersion silver Hi All, Why would someone choose thick immersion silver over thin? Are these different chemistries? Regards Steve Kelly Phone(O) (416) 750-8433 Phone (C) (416) 577-8433 If the recipient to whom this e-mail is sent has an NDA with PFC Flexible Circuits Limited this e-mail is considered confidential and is subject to any NDA agreements between the respective parties. See PFC on "How its' Made" in Canada on July 7th at 8 p.m. on the Discovery Channel ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________