Product integrity assessment using fatigue synthesis for avionicsprograms

摘要

The thermo-mechanical integrity of an electronics assembly isstrongly affected by the attachment method used between functionalcomponents and the printed wiring board. The use of solder as aninterconnect medium is the most common method in use today. In mostapplications, solder is required to serve multiple functions includingelectrical, thermal, and structural connection. Repetitive loads causedby thermal cycling and vibrations result in cyclical thermo-mechanicalstresses that often lead to pre-mature fatigue cracking in the solder.Continued exposure to these environments leads to degradation or failureof the solder thereby reducing the hardware's useful life. This paperpresents a novel method for predicting the fatigue life of anelectronics assembly by analyzing every interconnect using an automatedprocess modeling approach. Modular fatigue based routines, incorporatedthrough a user friendly software tool known as FSAP (Fatigue Synthesisfor Avionics Programs), facilitate concurrent design development andoptimization relative to the hardware's thermo-mechanical fatigueresponse. FSAP integrates the global effects from specific usageenvironments with the detailed design and process features associatedwith the electronics assembly. An application of FSAP along withcomprehensive model validation results from accelerated fatigue lifetesting is presented for a variety of common interconnect configurationsincluding leaded and non-leaded surface mount components and hybrid/MCMpackages