Study On Dynamic Mechanical Behavior Of SAC0307 Alloy At Macro-Micro Scale

With the rapid development of modern information technology,materials and processing technology in the field of microelectronic packaging are changing with each passing day.Low-Silver Lead-Free solder SAC0307,as an interconnected material between electronic components and circuit substrates,has comprehensive advantages over traditional Sn-Pb solder in terms of shear strength,wettability,ductility and electrical conductivity,and can meet the environmental protection requirements of completely lead-free in the field of electronic packaging,so it can gradually play an important role in replacing traditional lead-containing solder.However,the mechanical behavior characteristics of SAC0307 under extreme loadings such as high strain rate are not fully studied,and the plastic flow and hardening characteristics related to the strain rate under microscale are not reported,which greatly limits the development of its practical application.At the same time,with the increase of function density of portable electronic products,the design and manufacture of microscale of structural solder joint materials are demanding day by day,but there is a lack of experimental test means and basic theory to evaluate the dynamic mechanical properties of materials under microscale.In those connections,this master’s thesis carries out dynamic testing and FE calculation to provide basic test data for material’s popularization and use in the field of electronic packaging,meanwhile to provide a new test method and basic theory for the design and manufacture of microscale of metallic materials.First,it is found that the increase of strain rate will lead to the increase of material strength by static/dynamic compression tests of SAC0307.Under quasi-static loading,the increase of strain rate will lead to the acceleration of the high-speed rate of the stress value in the plastic flow stage,but the increase of strain rate under the dynamic loading mainly leads to the increase of plastic strain,and the effect on the flow stress is not obvious.At the same time,it is found that the magnitude of strain rate in the dynamic test is the root cause of thechange of plastic strain,not the length of the loading time.Then the Johnson-cook constitutive model parameters of SAC0307 are obtained by fitting the test data.Based on the theoretical analysis of the ability of the dynamic constitutive model to describe the rate-dependent mechanical behavior of the material,the model parameters are modified based on the adiabatic temperature rise phenomenon of the SAC0307 during dynamic compression.Finally,the FE model of the dynamic press-in of SAC0307 was established on the basis of the dimension optimization of the self-designed dynamic press-in experimental device.A mechanical calculation model for dynamic pressing test of metal materials is presented.The load-displacement relationship obtained by dynamic pressing test characterized by this model is verified by FE method.It is found that the plastic flow ability at microscale of the SAC0307 increases with the strain rate,and when the loading condition is fixed,the material will harden with the increase of the indentation depth,and the higher the indentation expansion rate,the more obvious the hardening characteristic is.