A Theoretical and Numerical study of crack propagation along a bimaterial interface with application to IC Packaging

Abstract

Based on a new second-order analysis, a modified crack surface displacement extrapolation method (MCSDEM) for evaluating interface delamination has been developed. The results show that using the proposed MCSDEM, the value of the total stress intensity factor agrees very well with the analytical solution. At the same time, based on crack closure theory and bimaterial interface crack theory, a new modified virtual crack closure method (MVCCM) for evaluating mode mixity has been developed. It is found that phase angle using the new equation matches well with exact solution under different loadings for a wide range of and appears to be unaffected by mesh size. MCSDEM and MVCCM are then used to investigate the effects of temperature, moisture diffusion and vapor pressure on the delamination in a plastic quad flat pack (PQFP) during tin-lead solder reflow and lead-free solder reflow. Finally, many end-notched flexure tests have been done at high temperature under different loading rates. It is found that for epoxy molding compound the critical energy release rate is rate dependent and the critical energy release rate increases with the loading rate.