Thankyou, Werner and all who replied to this question. This application is expected to see temperature variation from -20C to 100C. However, this will be operating environment changes at low rate of change. From what you say, the main concern is rate of change/ frequency of cycle that will reduce reliability, rather than the high maximum temperature. regards, Phil. At 08:49 5/09/00 -0400, you wrote: >Hi Phil, >Some of the responses you received do not answer your question. > >We are designing a Printed Board Assembly that will be required to operate > >in an ambient temperature up to 100 degrees Centigrade. > >There have been concerns expressed about the strength of solder joints at > >that temperature. >The answer is no, the strengths of solder joints, provided they are properly >wetted and not sufficiently damaged by fatigue, is never an issue. The >strength of the solder joints is adequate even in severe vibration and >mechanical shock loading. The 'stress due to thermal mismatch' is also not an >issue, since solder joint fatigue is strain-driven, not stress-driven. That >means that the total creep-yield plastic deformation in solder joints will be >the same for equal delta-Ts, but at higher Ts the creep process will be >completed faster. This has a consequence in accelerated testing, but not for >product in functional use. >As Dave Hillman pointed out however, if you cycle from some lower T to this >high T of 100C, you will get more creep-fatigue damage per cycle than for >T-excursions to lower maximum temperatures; thus, earlier fatigue failures >would occur in your situation. Whether this will give you adequate >reliability depends on the design and use details. > >Werner Engelmaier >Engelmaier Associates, L.C. >Electronic Packaging, Interconnection and Reliability Consulting >7 Jasmine Run >Ormond Beach, FL 32174 USA >Phone: 904-437-8747, Fax: 904-437-8737 >E-mail: [log in to unmask], Website: www.engelmaier.com > >############################################################## >TechNet Mail List provided as a free service by IPC using LISTSERV 1.8d >############################################################## >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://www.ipc.org/html/forum.htm) for additional >information. >If you need assistance - contact Keach Sasamori at [log in to unmask] or >847-509-9700 ext.5315 >############################################################## Phil Dutton C.I.D. Senior CAD Technician IPC Certified Interconnect Designer Tenix Defence Systems Pty Ltd Systems Division - Adelaide Second Avenue, Technology Park, Mawson Lakes. SOUTH AUSTRALIA 5095 ================================ Phone: (08) 8300 4400 (reception) Fax: (08) 8349 7420 email: [log in to unmask] Internet Page: http://www.tenix.com ================================ ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8d ############################################################## 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://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################