Don't forget the collateral damage. Not only is the surface finish and therefore solderability degraded by repeated soldering, the adjacent interconnect structures and the dielectric material in that area of the board are also degraded by those same thermal excursions. It would be a heck of a thing to have a component perfectly soldered, after the fifth rework, to an open circuit. How much are the adjacent interconnect structures and dielectric materials degraded by repeated soldering? ... it depends. "Survivability" testing of representative coupons may be helpful. Sincerely, Paul Reid Program Coordinator PWB Interconnect Solutions Inc. 235 Stafford Rd., West, Unit 103 Nepean, Ontario Canada, K2H 9C1 613 596 4244 ext. 229 Skype paul_reid_pwb [log in to unmask] <mailto:[log in to unmask]> -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Joe Macko Sent: Friday, May 23, 2008 1:41 PM To: [log in to unmask] Subject: [TN] Methodology for determining the # of reworks ENIG finished solder lands for leaded components can withstand Techs, I am looking for some help / guidance on how to analytically determine the number of times the same leaded component can be replaced on a ENIG finished board before the solder lands located on the PCB have been degraded beyond their capability to provide a solderable class 3 surface (.e., how many times can the ENIG finished solder lands with stand a rework/component remove & replace). I suspect the dissolution rates of nickel and copper come into play however I am not sure how to approach this issue and suspect there are some relatively straightforward formulas out there to accomplish this task. Everyone has a different idea and there are numerous rules of thumb discussed but I would like to try something more analytical (without having to use a supercomputer). Thanks again and everyone enjoy the long weekend. Best Regards, -joe --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------