We have been debating the proper dwell time for thermal cycling tests. Per IPC-SM-785 it should be 15 minutes (min.). Indeed the majority of publicized thermal cycling tests use dwells of 10-20 minutes. However, there are camps that advocate longer dwells (min 30min.) to sufficiently account for the effects of creep fatigue in solder joints. What rational/assumption was used for defining the minimum dwell time for space applications in IPC-785? Would longer dwell durations significantly change the cycles-to-failure results? What factors would have to be considered to assess any compromises? For reference, our target application is space-borne. Thermal cycling extremes are -55C and +125C. CTEs between parts & PWB will be matched to <5ppm/C difference. --------------------------------------------------------------------------------- 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 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 ---------------------------------------------------------------------------------