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
-----------------------------------------------------