I've been reading IPC-D-279 with great interest. However, I get a little more confused about thick IMC layers especially after reading the following: IPC-D-279 A-3.3 CAVEAT 1 ? SOLDER JOINT QUALITY The solder joint fatigue behavior and the resulting reliability prediction equations. Eqs. A-1 through A-2, were determined from thermal cycling results of solder joints that failed as a result of fracture of the solder, albeit sometimes close to the IMC layers. For solder joints for which layered structures are interposed between the base material and the solder joints, these equations could be optimistic upper bounds if the interposed layered structures become the ?weakest link? in the surface mount solder attachments. Such layered structures could be: metallization layers that have weak bonds to the underlying base material, or are weak themselves, or dissolve essentially completely in the solder; oxide or contamination layers preventing a proper metallurgical bond of the solder to the underlying metal; brittle IMC layers TOO THICK due to too many or improperly long high temperature processing steps. Guenter, I'm sure you, Werner, and Dave H. and all others on this planet can end my pain. I'm talking, of course, about the last, very long paragraph in the caveat. MoonMan --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------