Research On Mechanical Properties Of Meso Damage Of Sn3.0Ag0.5Cu Material

96.5Sn3.0Ag0.5Cu(SAC305)material is a kind of common lead-free solder used in microelectronic packaging solder joints,based on micro damage mechanical theory,considered the micro void evolution effect,SAC305 material properties and the damage and failure mechanism of joint in service are studied.Based on the experimental research,combined with the fitting method,we determine the Gurson-Tvergaard-Needleman(GTN)constitutive model parameters of micro damage mechanics,and verified the validity of the model by comparing the stress and strain response data with the experimental data in the constant strain loading conditions.The main contents of this paper are:(1)In order to obtain the performance of the real service,the simulation reflow soldering test platform is built,and the SAC305 welding wire for reflow environment are simulated,through finite element simulation and experimental measurement,regulate and control the temperature change curve of reflow oven,and the change of welding wire surface is observed by scanning electron microscope(SEM).(2)Using the SAC305 wire with the diameter of 200?m into the uniaxial tensile test,select six different strain rates,we get the load-displacement curve and calculate the true stress-strain curve,determine the initial yield strain and yield limit;subsequently,substitute the known parameters into the GTN constitutive equation,and use the simulated annealing algorithm to calculate the unknown parameters;establish a finite element model of wire,substitute the calculated nine parameters into the ABAQUS software for finite element analysis,identify and optimize the constitutive model parameters of GTN until get the optimal solution.(3)According to the determined damage parameters,and by using user-defined material subroutine UMAT,the modified GTN micro damage constitutive model is applied into the environment of the finite element software ABAQUS.In thermoelectric coupling,analyse lead-free solder joint temperature changes and pore structural changes,and predict the failure position of the critical solder joints and compare it with the SEM results.