| With the development of electronic information industry, electronic packaging structures and systems are moving towards miniaturization, intergration, low-power and high reliability.Corresponding electronic packaging structures are even more complicated and the application environment is getting worse. Especially in high reliability area, inevitably affected by temperature, vibration, impact and other factors in the process of transferring and using, electronic packaging structures get failure. Usually, solder joint is the most fragile part in packaging structures. The solder’s failure is the major factor of electronic packaging’s failure. Therefore, the research of solder’s feature and constitutive model is of great theoretical value to analyze solder joint’s capability and accurately predict reliability of electronic packaging. Meanwhile, with the release of lead ban by various countries and regions, lead-free solder to replace the traditional tin-lead solder has become an inevitable trend. However, the constitutive model, material parameters of lead-free solder, and the impact analysis of loading rate, etc. on mechanical behavior are far from perfect and research is still lacking. Related researches about constitutive model of lead-free solder and parameter identification method are performed in the thesis.A viscoplastic Anand damage constitutive model with deformation-damage coupled is established by introducing an isotropic damage variable to the Anand constitutive equation in the first part of this thesis. The evolution equation of damage variable is deduced in thermodynamic framework. The model was implemented into finite element software ABAQUS for finite element simulation through user material subroutines UMAT.The model and user subroutine are verified by finite element simulation calculation.Besides, it is concluded that damage variable changes when material damage changes during loading. The conclusion can be used for analysis of material life based on the relation between loading and damage.A global parameter sensitivity analysis method of constitutive model is established based on improved Symmetric Latin Hypercube Sample and Spearman rank correlation coefficient in the second part of this thesis. The parameter sensitivity analysis program is compiled by combining MATLAB and ABAQUS. The global parameter sensitivity analysis of lead-free solder Sn4.0Ag0.5Cu’s viscoplastic Anand damage constitutive model is processed. The sensitivity and rank of each parameter are determined. The impact of sensitivity by model size, loading, result data type, loading rate is discussed. The conclusion can be used for determination of parameter identification method and experiment conditions.Tensile tests of lead-free sloder Sn4.0Ag0.5Cu wire are carried out by displacement load form under four different loading rates, 0.0002/s, 0.001/s, 0.005/s, 0.01/s, at normal temperature inthe third part of this thesis. The strain rate correlation and sensitivity of lead-free sloder Sn4.0Ag0.5Cu’s deformation behavior are discussed on the basis of test data. The loading-displacement data is transformed to stress-strain data for parameter identification of constituvite model.A mathematical model of constituvite model’s parameter identification is built in the fourth part of this thesis. A parameter identification method of constituvite model is established by combining genetic algorithm and ABAQUS on the basis of the mathematical model. With the method, the viscoplastic Anand damage constituvite model’s parameters of lead-free sloder Sn4.0Ag0.5Cu are identified. The comparision between viscoplastic Anand damage constituvite model and Anand constituvite model on sloder’s simulation is made. It is concluded that the curve simulated by viscoplastic Anand damage constituvite model is closer to the test curve. The stiffness degradation phenomenon can be described more accurately. The rationality of adopting the deformation-damage coupled model in solder’s mechanical behavior simulation is verified.In the beginning of the fifth part, the traditional genetic algorithm is parallel processed via multiple parallel structure. The multi-population genetic algorithm is improved by optimization strategies. A parameter identification method based on the multi-population genetic algorithm is built. The viscoplastic Anand damage constituvite model’s parameters of lead-free sloder Sn4.0Ag0.5Cu are identified through the method. The result demonstrates the feasibility and accuracy of the method. The convergence rate, searching ability and overcoming premature are superior to traditional genetic algorithm.
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