Roger, A very good place to start is the proceedings of Surface Mount International for 1994 and 1995. There are several articles that present data on this very topic. It is interesting to review the 1995 articles after reading the 1994 stuff. Some of the concerns regarding solder joint cracking that existed in 1994 appear to have been shown to be non-problems? by 1995. Look particularly for articles by Compac Computer Corporation. You might also consider articles that describe the use of an epoxy underfill to reduce thermal-expansion induced joint cracking. Hopefully some folks from Motorola and IBM will respond to your inquiry as well. I have seen data that predicts lifetimes of BGA solder joints in typical commercial product environments. For what its worth: We have been conducting joint lifetime tests with very small, 10-mil diameter "solder domes", over the last couple of years. Epoxy underfill clearly reduces solder joint failure. And just like Motorola and IBM have advertised...the solder assembly reliability of this packaging scheme is very good. Even the mini-BGAs we have been building (10-mil diameter x ~ 4-mil high domes on 20-mil pitch) are quite easy to solder reliably. For more information regarding the work Sandia Labs is doing, contact Keith Treece at email: [log in to unmask] phone: 505-844-9684 Gary P. --- Gary D. Peterson _/_/_/ _/ _/ _/ SANDIA NATIONAL LABORATORIES _/_/_/ _/ _/_/ _/ _/ P.O. Box 5800, M/S 0503 _/_/ _/_/_/ _/ _/ _/ _/ Albuquerque, NM 87185-0503 _/_/_/_/_/_/ _/ _/ _/_/ _/ Phone: (505)844-6980 _/ _/_/ _/ _/_/_/ _/ _/ _/_/_/_/ FAX: (505)844-2925 _/ _/_/ _/ E-Mail: [log in to unmask] _/_/_/