In a message dated 98-04-24 18:05:55 EDT, you write: << We use both, depending on the test specification, so I am curious, how do the damage and/or failure mechanisms differ between thermal cycling and temperature cycling? >> Heidi, Air-to-air thermal cycling (or single chamber cycling) and liquid-to-liquid "thermal shock" can both lead to solder joint fatigue. For supporting evidence, see (for example) detailed failure mode analysis in the following papers: 1) Darveaux, R., Banerji, K., Mawer, A. and Dody, G., "Reliability of plastic ball grid array assemblies", Chap. 13, Ball Grid Array Technology, ed. J. H. Lau, McGraw-Hill, 1995, pp. 379-442. 2) Frear, D. R., "Microstructural evolution during thermomechanical fatigue of 62Sn-36Pb-2Ag and 60Sn-40Pb solder joints", Proceedings, 40th Electronic Components and Technology Conference, Las Vegas, NV, May 11-13, 1990, Vol. 1, pp. 518-524. 3)Frear, D., Grivas, D. and Morris, J. W., "Parameters affecting thermal fatigue behavior of 60Sn-40Pb solder joints", Journal of Electronic Materials, Vol. 18, No. 6, 1989, pp. 671-680. Liquid-to-liquid transfer from -55C to 125C lead to solder joint fatigue failures similar to failures in air-to-air thermal cycling. When interfaces and metallizations are the weakest links (for either mechanical or chemical / cleanliness reasons), they may also fail under both types of test. Mechanical cycling is also used and provides useful information. When boards are subject to isothermal cyclic twist, for some devices you get solder joint fatigue failures, for others the leads may break. By raising the test temperature, lead failures can be eliminated and solder joints will fail. So, there is no single answer to your question. Whatever the test, the best way to find out what mechanism is being accelerated is to conduct a thorough failure mode analysis. With experience on your company's products, and by looking at your company's accelerated test database, you probably can tell what test conditions are right for the requirements of your application. Regards, Jean-Paul ________________________________________________ Jean-Paul Clech EPSI Inc., P. O. Box 1522, Montclair, NJ 07042 SMT / BGA / Flip-Chip / CSP reliability specialists tel: (973)746-3796, fax: (973)655-0815 home page: http://members.aol.com/Epsiinc1/index.html (last updated on April 23, 1998) ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################