Tuning damage model to optimize the plastic strain distribution in electronic packaging structures

Due to the cyclic loading of thermal stress, the solder joints work in the process of cyclic fatigue, and the failure behavior of solder joints in the whole process is actually a process of damage accumulation. It is feasible to study the fatigue properties of solder joints under cyclic loading. In order to achieve accurate numerical simulations, solder constitutive models have been widely concerned. The method of coupling damage variables with a constitutive model provides an effective way to achieve this goal. Under the condition of thermal cycle loading, the damage evolution corresponding to deteriorate material properties meets the basic principle framework of thermodynamics. In this framework, the damage evolution model can be derived by using continuum damage mechanics. This model is greatly simplified by averaging the micro defects of materials, as long as the established model and its derived evolution model can solve engineering problems. Based on the theoretical framework of damage constitutive model, a UMAT user material subroutine suitable for ABAQUS finite element software is completed. Through the secondary development interface of ABAQUS, the viscoplastic constitutive model parameters of coupling damage are continuously optimized, so as to achieve better simulations of the solder fatigue process. Based on the study of the coupled damage constitutive model, the UMAT is applied to the calculation of BGA packaging structure to further reflect the optimization capacity of the model for solder fatigue performance with simulation results as a good fit to the test results.