Phil, John I looked a bit in good ol' Klein Wassink and found his formula for the growth of intermetallic compounds on Cu surfaces: d=10^3(exp(-5*10^3/T)t^1/2 d= Thickness of IMC in um T= Temperature in K t= time in sec. The equation can easily be solved for t. Gives a nice Excel spreadsheet where the time for a given temperature can be estimated a layer of Sn of a certain thickness needs to be transformed to IMC and will thus make problems in soldering. Gives interesting results when Sn 0.8um is compared with 1.2um thickness. Guenter EMPA Swiss Federal Laboratories for Materials Testing and Research Centre for Reliability Guenter Grossmann, Senior Engineer 8600 Duebendorf Switzerland Phone: xx41 1 823 4279 Fax : xx41 1 823 4054 mail: [log in to unmask] --------------------------------------------------- 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 -----------------------------------------------------