I don't believe in models for soldering.. I'm a gaggy old dog that like hands on. I use to start tempcycling and life tests immediately. Such tests do not tell the whole truth either, but safer than models. Models tend to indealize terms and factors, but reality is more like a mustang. Hard to catch, hard to tame. A collegue here has developed a model for BGA solder joints, pages and pages with math, and he is very ambitious and loves what he is doing. We implemented his huge model for some boards, but the result of the simulations was so diverging and indistinct that we couldn't figure out what could be presented to our customer. I think the problem lies in the very invidual characters of solder joints, like leaves on a birch..all are different even if they look similar. Inge -----Ursprungligt meddelande----- Från: TechNet [mailto:[log in to unmask]] För Werner Engelmaier Skickat: den 16 november 2005 16:49 Till: [log in to unmask] Ämne: Re: [TN] [LF] Reliability prediction of LF soldering Hi Ofer, I certainly know what MTTF and MTBF means, and for some things these concepts work--MIL-HDBK-217 was built on them. However, for solder joints this is different and that is why MIL-HDBK-217 does not work for solder attachments. Solder joints are not equally loaded [the one's on the corners see significantly more loading, everything else being equal]--that is why one always deals with all the solder joints on a component. The solder joints on various components have different loading conditions as well depending on component size, solder joint geometry, and component power dissipation. The life of a compont's solder attachment [all solder joints] is measured in terms of cycles not time per se. That is why reliability models need to exist to determine an estimate of the fatigue life of the solder attachments. There have to be different models for leadless and leaded solder joints [here lead has nothing to do with Pb] and different models for different solder alloys. We simply do not have the data at this point for Pb-less solders to develop fatigue reliability models. Regards, Werner Engelmaier Engelmaier Associates, L.C. Electronic Packaging, Interconnection and Reliability Consulting 7 Jasmine Run Ormond Beach, FL 32174 USA Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904 E-mail: [log in to unmask], Website: www.engelmaier.com --------------------------------------------------- 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 -----------------------------------------------------