Numerical Simulations for Reliability Assessment of Lead-Free Solder Interconnections in BGA Packages

Aalto University, P.O. Box 11000, FI-00076 Aalto www.aalto. fi Author Jue Li Name of the doctoral dissertation Numerical Simulations for Reliability Assessment of Lead-Free Solder Interconnections in BGA Packages Publisher School of Electrical Engineering Unit Department of Electronics Series Aalto University publication series DOCTORAL DISSERTATIONS 48/2011 Field of research Electronics Production Technology Manuscript submitted 7 February 2011 Manuscript revised 16 May 2011 Date of the defence 21 June 2011 Language English Monograph Article dissertation (summary + original articles) Abstract This work presents the results of computer-aided numerical simulations for the reliability assessment of lead-free solder interconnections in BGA packages. The finite element and Monte Carlo methods were employed for the macroscale structural and the mesoscale microstructural simulations, respectively. The major reliability tests for electronic component boards, i.e. thermal cycling, power cycling and drop impact tests, were simulated via the finite element method. The results provide a feasible tool for a better understanding of the observed failure modes in the reliability tests. The lifetime predictions based on the simulation results are helpful for the lifetime estimations of the BGA packages. The temperature effects on the drop impact reliability of the BGA packages were successfully elucidated by the finite element numerical experiments. In addition, a new algorithm was developed in order to predict dynamic recrystallization in solder interconnections during thermal cycling. The approach was realized by combining the Potts model based Monte Carlo method and the finite element method. The correlation between real time and Monte Carlo simulation time was established with the help of the in situ test results. Recrystallization with the presence of intermetallic particles in the solder matrix was simulated by introducing the energy amplification factors in the particle-affected deformation regions. The present algorithm predicted both the incubation period of the recrystallization as well as the growth tendency of the recrystallized regions in a way consistent with the experimental findings.This work presents the results of computer-aided numerical simulations for the reliability assessment of lead-free solder interconnections in BGA packages. The finite element and Monte Carlo methods were employed for the macroscale structural and the mesoscale microstructural simulations, respectively. The major reliability tests for electronic component boards, i.e. thermal cycling, power cycling and drop impact tests, were simulated via the finite element method. The results provide a feasible tool for a better understanding of the observed failure modes in the reliability tests. The lifetime predictions based on the simulation results are helpful for the lifetime estimations of the BGA packages. The temperature effects on the drop impact reliability of the BGA packages were successfully elucidated by the finite element numerical experiments. In addition, a new algorithm was developed in order to predict dynamic recrystallization in solder interconnections during thermal cycling. The approach was realized by combining the Potts model based Monte Carlo method and the finite element method. The correlation between real time and Monte Carlo simulation time was established with the help of the in situ test results. Recrystallization with the presence of intermetallic particles in the solder matrix was simulated by introducing the energy amplification factors in the particle-affected deformation regions. The present algorithm predicted both the incubation period of the recrystallization as well as the growth tendency of the recrystallized regions in a way consistent with the experimental findings.