Pratap, I would caution the use of your equation without further information about the use environments and design conditions. The exponent you cite is actually the negative inverse of the plastic fatigue ductility exponent as defined by ASTM fatigue standards. If the PCB design and use environment induce plastic strains in the solder joints than your equation may be valid. But, if the design and use environment do not strain the solder joint enough to cause plastic strains (i.e. the design induces elastic strains) than you must consider an elastic plastic fatigue model for comparing the damage. In other words, your test condition is probably causing plastic strains while the use condition may cause elastic strains. Using a purely plastic fatigue equation to compare the damage between the two conditions may give very misleading results. -- Karl Sweitzer Eastman Kodak Company voice: 716.47.77546 800 Lee Road fax: 716.47.77293 Rochester, NY 14650-3118 mailto:[log in to unmask] ################################################################ 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################