A hybrid approach to characterization and life assessment of trilayer assemblies of dissimilar materials under thermal cycles

Alireza Shirazi, Ryerson University

Date of Award

2011

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

First Advisor

H. Lu

Second Advisor

A. Varvani-Farahani

Abstract

The current study puts forward non-local closed-form solutions for interfacial peel and shear stress, as well as warpage deformation, of trilayer structures under thermal cycling. Based on the solution, a hybrid experimental-analytical inverse method (HEAIM) has been proposed for characterizing the constitutive behaviour of the trilayer constituents. The method is applied to optimize the correlation between the experimentally measured thermal warpage of a trilayer structure and the analytically solved warpage. Furthermore, a localized analytical and experimental method is suggested for characterizing the stress-strain relation of a joint alloy at the interfacial level in the trilayer structure. The resulted viscoelastoplastic model of the joint alloy is further employed in predicting the life of a trilayer structure that consists of a failure dominant adhesive layer made of the same joint material. A method for the thermal figure fatigue life prediction is proposed, which applies critical plane-energy fatigue damage parameter in combination with a modified Coffin-Manson life model. The experimental evaluation of the proposed models and approaches for the characterization of thermally induced trilayer structure deformation and stress, as well as the fatigue life prediction is conducted on several custom-made trilayer structures as well as real microelectronics. In the study if trilayer structure reliability and durability, experimental validation of numerical and analytical modeling has been rare. The current study has obtained good agreement between the measured trilayer warpage and the predicted one using the thermomechanical properties of the trilayer constituents determined by HEAIM, owing to its more accurate prediction for the creep behaviour of the joint alloy. The study of thermal fatigue of the trilayer structure follows a new method that involves the critical plane-energy fatigue damage parameter. The resulted fatigue life prediction has been promising.