Prognostication of system-state in lead-free electronics equipment under cyclic and steady-state thermo-mechanical loads

In this paper, a mathematical approach for interrogation of system state under cyclic thermomechanical stresses has been developed for three-different leadfree solder alloy systems. Data has been collected for leading indicators of failure for alloy systems including, Sn1Ag0.5Cu, Sn3Ag0.5Cu, Sn4Ag0.5Cu second-level interconnects under the application of cyclic thermo-mechanical loads. Methodology presented resides in the pre-failure space of the system in which no macro-indicators such as cracks or delamination exist. Systems subjected to thermomechanical damage have been interrogated for system state and the computed damage state correlated with known imposed damage. The approach involves the use of condition monitoring devices which can be interrogated for damage proxies at finite time-intervals. Interrogation techniques are based on non-linear least-squares methods. Various techniques including the Levenberg-Marquardt algorithm have been investigated. The system´s residual life is computed based on residual-life computation algorithms. Detection of system-state significantly prior to catastrophic failure can significantly impact the reliability and availability of electronic systems. Requirements for system availability for ultrahigh reliability electronic systems are driving the need for advanced heath monitoring techniques for early detection of onset of damage. Traditional health monitoring methodologies have relied on reactive methods of failure detection often providing little on no insight into the remaining useful life of the system.