Dear Werner: MIT the university is in Cambridge, however us Master IPC Trainers are all around you.... Gregg -----Original Message----- >From: Werner Engelmaier <[log in to unmask]> >Sent: Mar 16, 2007 11:53 AM >To: [log in to unmask] >Subject: Re: [TN] SMT Solder Joint Strength > >Hi Gregg, >Last I looked MIT was in Cambridge. >Solder joint strength is never the issue with a properly 'wetted' solder >joint. Under sufficient force you will rip the soldering pad out of the resin >matrix, but not separate the solder joint. >The strength, or more accurately the yield strength, comes into the picture >when thermal cycling, because the yield strength is highly >temperature-dependent [as are almost all other properties of solder]. >When T-cycling leadless solder joints the cyclic stress range will be bounded >by the yield strength of the solder at the prevailing T; the reason why >compliant leads work is that they do not allow the stress range to come close to >the yield strength=f(T). >The high variability of lead geometries, and some of the above, make SJ >strength standards impractical to say the least, and even if you could do it, what >would you do with the information? >What is much more important is the failure mode—either brittle interfacial >showing there is something wrong with the SJ arrangement, or pad rip-out >meaning the SJ is good. > >Werner >P.S.: Bev, which part of the above do you disagree with? > > > >************************************** > AOL now offers free email to everyone. Find out more about >what's free from AOL at http://www.aol.com. > >--------------------------------------------------- >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 -----------------------------------------------------