Tension-Compression Fatigue Damage Study By SAC405Lead-free Solders

In view of the detriment of lead to human survival environment and physical health, and the provisions of the global lead-free legislation, using lead-free solder instead of lead solder in the electronic industry has become inevitable trend. The reliability of lead-free solder for electronic product quality is extremely important. Therefore, understanding and mastering the mechanical properties, constitutive behavior and failure mechanism of lead-free solder is one of important research direction of ensuring solder and its structure use efficiently.This article selects the SAC405lead-free solder as the research object. Firstly, this article introduced two constitutive models of solder, that is, unity type Anand constitutive model and separation type constitutive model, including the basic theory of the model, the method of confirming parameters and two kinds of model parameters of SAC405lead-free solder. And then doing the tension-compression low cycle fatigue experiments of SAC405lead-free solder in different temperatures, different strain amplitudes and different loading frequencies. This article analyzes the fatigue failure characteristic of solder at tension-compression cycle load and discusses the variation pattern of its peak stresses, stress amplitudes and plastic strain energy densities and so on. The result shows that, SAC405lead-free solder performance for obvious cyclic softening characteristics, and its parameters such as peak stress, stress amplitude and plastic strain energy density etc. with the rise of number of cyclic and decrease. The stress amplitude and plastic strain energy density of the solder with the rise of loading frequency and decrease, with the rise of temperature and decrease, and their decline rate with the increase of strain amplitude and decrease.Using the Manson-Coffin formula fitted the fatigue life of SAC405lead-free solder, determined the fatigue parameters that related to temperature. According to Lemaitre damage theory, using the isotropic damage and analyzing the fatigue damage characteristics and damage evolution law of solder, reaching out the critical damage threshold and damage parameters of SAC405lead-free solder. Using the numerical simulation of three visco-plastic constitutive models, that is, unity Anand model, isotropic hardening separation model and kinematic hardening separation model simulated the mechanical behavior of solder at cycle load. Finally, using kinematic hardening separation model simulated the tension-compression low cycle fatigue experiments of SAC405lead-free solder, the results and experimental value are comparatively identical, verified the effectiveness of the fatigue damage formula parameters.