In a message dated 4/29/2008 4:19:24 A.M. Eastern Daylight Time, [log in to unmask] writes: I need to be able to predict the fatigue life of solder joints under different thermal cycling and vibration load conditions. The PCB will usually be FR4, the solder tin/lead, the components everything from BGA's to chip passives. Ideally I need to provide an estimate on cycles to failure. While many of us on TechNet can help you some, I too do not think there is exact empirical software. Fortunately, you are using tin/lead where there is a lot more data, and working models. I can give you the following personal observations from both the IPC Relaibility Conference two weeks ago in Boston, and from our project advising Crane Naval Depot on repair of interconnections in the face of the lead-free avalanche: 1. Werner Engelmaier (and other consultants) can use projections from fatigue equations to estimate first failure, assuming the input data is correct. I am assuming you want estimated first failure, not some statistical representation like when 10% failure or 50% failure. His presentation is posted from that conference, but since it was for a fee by IPC, the presentation posting on the IPC site is their property. 2. From our project analysis of many Weibull plots, we generalize that the smaller the solder joint volume, the earlier the failure. BGAs and worse - QFNs - are now getting a lot of publicity, because they are the first to fail in thermal or vibration situations. 3. Vibration is a less exact science than Thermal cycle. What kind of use condition are you dealing with? We are quite concerned about military electronics in high vibration conditions where stiffer Lead-Free solders may be used. Tests show that component location on boards is very important, as BGAs can either be almost instantly failed, or can perform admirably, depending on assembly location on a vibrating board. 4. FR4 is not always plain old FR4 in either thermal cycling or vibration testing. Much of the newer, high temperature laminate is FR4, but has different modulus and possibly even different moisture absorbsion, that effects mechanical properties of the solder joints attached. Fortunately for Crane, most military repair is on older 140 Tg boards that are not as stiff as the newer laminate that can sustain highter soldering temperatures. The prior recommendations for consultants and working consortia could be quite helpful. Dennis Fritz SAIC, Inc. **************Need a new ride? Check out the largest site for U.S. used car listings at AOL Autos. (http://autos.aol.com/used?NCID=aolcmp00300000002851) --------------------------------------------------- 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 -----------------------------------------------------