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A Fracture Mechanics Approach to Thermal Fatigue Life Prediction of Solder Joints
Published online by Cambridge University Press: 25 February 2011
Abstract
The approach developed is based on the assumption that thermal fatigue crack propagation in solder joints is primarily controlled by C* and J integrals. The effect of microstructural coarsening on crack propagation is discussed. A fracture criterion, J≥Jc, is used to define the failure of the joints. A crack growth governing equation has been formulated and can be numerically integrated to obtain the crack growth history given stress history as an input. The approach was applied to model the experiment by Wong and Helling [15]. In their experiment, surface-mounted electronic devices using eutectic Pb/Sn solder were tested in thermal cycles of −20 to 100°C and −55 to 125°C. A unified constitutive equation was assumed for the eutectic Pb/Sn solder. An equation for solving the shear stress in the joint was formulated and is coupled with the crack growth equation. Both equations were solved simultaneously by the Runge-Kutta method for the stress-time and crack growth history. The results of the prediction are in a good agreement with the experimental data, which indicates that fracture mechanics may be applied to describe the failure process of solder joints under cyclic thermal loadings.
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- Copyright © Materials Research Society 1991
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