Author: Jacob Welch
Date/Time/Location: April 24th, 1:30-3PM, ERF 1207.
Title of Thesis: Spectral Methods of Modeling and Calculating Fatigue in Electronic Interconnects
List of Committee Members:
Abhijit Dasgupta (Chair)
Michael Osterman
Avik Dutt
Abstract:
The purpose of this thesis is to provide a predictive estimate of fatigue damage accumulation in PWA interconnects using purely frequency-domain (spectral) information such as the PSD of the input excitation. This method is used to predict fatigue damage accumulation rate in the critical interconnects, for broad-band random vibration excitation on a PWA with LQFP components. Results are compared with those obtained from a direct time-domain approach. The modeling is achieved using a two-stage global-local modeling process in Abaqus, where the dominant mode shapes of the dynamic global model are applied to a 3D quasi-static local model, using multi-point constraint equations. The transfer function from PWB strain to interconnect strain is then estimated for each of the dominant modes. The PWB response PSD from the global model is then used in conjunction with these strain transfer functions, to estimate the PSD of the strain response in the critical lead/solder for each dominant mode, and summed over each mode, and then used to reconstruct a pseudo-time history of lead strain. This pseudo time history is then used to perform a Rainflow cycle count. From this point established methods are able to be used to estimate fatigue damage accumulation using either the cyclic count or with competing methods such as Rayleigh method or Dirlik method. Results are compared to corresponding fatigue damage estimates from a time-domain analysis method.