PSI - Issue 2_B

V. N. Le et al. / Procedia Structural Integrity 2 (2016) 2614–2622 V. N. Le / Structural Integrity Procedia 00 (2016) 000–000

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5. Conclusions In this work, a numerical methodology is proposed for reproducing the intergranular fatigue crack in the critical zone of the solder joint. The submodelling technique has been used to reduce the computational cost of the simulations. The global model of the power module is fist simulated with the bulk material properties of all the components to find both the critical zone in the solder joint and the boundary conditions to be applied to the submodel of the module. In the submodel, the solder joint is reconstructed at grain structure level using a crystal plasticity model for the grains and cohesive elements for the grain boundaries. The parameters for crystal plasticity of the lead-free solder are calibrated using the Berveiller-Zaoui transition rule to fit tensile test data, while the cohesive zone parameters are obtained using some assumptions on the stiffness of the interface and its energy. It was demonstrated that the developed methodology could successfully reproduce the intergranular crack initiation and propagation in the solder joint during fatigue loading. Damage initiates at intersections of grain boundaries at the external surface. The dominant crack develops from the corner of the solder layer near the bottom interface and propagates towards the interior, in accordance with previous experimental observations. Another interesting result obtained in this work is the nearly stable crack propagation rate through the grain boundaries of the solder alloy during the thermal loading cycles. This suggests that the global fatigue lifetime of the solder joint can be predicted by simple extrapolation from quantities obtained in the local model. Acknowledgements We want to express our gratitude in particular to Jean Michel MORELLE and Philippe POUGNET from VALEO for their general advice. Lu, H., Bailey, C., Yin, C., 2009. Microelectronics Reliability Design for reliability of power electronics modules, Microelectron. Reliab. 49 1250– 1255. Celnikier, Y., Benabou, L., Dupont, L., Coquery, G., 2011. Investigation of the heel crack mechanism in Al connections for power electronics modules, Microelectron. Reliab. 51, 965–974. Benabou, L., Le, V.N., Sun, Z., Pougnet, P. , Etgens, V., 2014. Effects of voids on thermal-mechanical reliability of lead-free solder joints, MATEC Web Conf. 12, 04026. Beyer, H., Sivasubramaniam, V., Hajas, D., Nanser, E., Brem, F., 2014. Reliability Improvement of Large Area Soldering Connec- tions by Antimony Containing Lead-Free Solder, 1–8. Lee, W.W., Nguyen, L.T., Selvaduray, G.S., 2000. Solder joint fatigue models : review and applicability to chip scale packages, 40, 231–244. Anand, L., 1985. Constitutive equations for hot-working of metals, I, 213–231. Gong, J., 2008. Mesomechanical Modelling of SnAgCu solder joints in flip chip, Comput. Mater. Sci. 43, 199–211. Bieler, T.R., Telang, A.U., 2009. Analysis of slip behavior in a single shear lap lead-free solder joint during simple shear at 25°C and 0.1/s, J. Electron. Mater. 38, 2694–2701. References