Dynamic Mechanical Properties Of Sn0.3Ag0.7Cu Solder Based On Dynamic Indentation Test

With the development of electronic industry,the size of portable electronic products is getting smaller and smaller,which leads to the size of electronic devices decreasing gradually.The solder joints which play the role of mechanical support and electrical signal transmission in electronic packaging are becoming smaller and smaller,even reaching micron and nanometer scales.In addition,the low silver lead-free solder has better ductility and lower cost than the high silver lead-free solder.Now the low silver lead-free solder is more and more important in electronic products.The service environment of electronic products is becoming more and more complex.During transportation and use,they will always be impacted and dropped,or they will be in a high temperature environment.Therefore,it is particularly important to study the mechanical properties of micro-structured solder joints under impact and high temperature environment.Based on the above problems,the mechanical properties of low silver lead-free solder Sn0.3Ag0.7Cu were studied as follows:1.Based on Hopkinson pressure bar technology and the principle of static nanoindentation test,a dynamic indentation test system is designed and optimized.This paper discusses and solves many key problems such as overloading the specimen due to excessive momentum of the equipment,output of test data,pressure acquisition and so on,and completes the erection of dynamic nanoindentation test bench.The load-displacement relationship of dynamic indentation test system under different strain rates is derived for the first time the dynamic characteristics of microscale materials at high strain rates can be tested by further improvement Based on Hopkinson pressure bar technology and static nanoindentation principle.The dynamic indentation process of solder is simulated by finite element method,and the load-displacement relationship is obtained.The displacement and the basic equation are used to deduce the load,which are in good agreement with the calculated values,and the validity of the theoretical deduction is verified.2.The dynamic indentation test of low silver lead-free solder was carried out with self-designed experimental device,and the load-displacement curves of solder at different loading rates were obtained.The load-displacement curve is stable when.the pressure is high.The load-displacement curve fluctuates greatly When the air pressure is insufficient.The effects of different constitutive models of low silver lead-free solder on Mises stress and load-depth curves of low silver lead-free solder were analyzed by finite element method.It was found that the constitutive model considering strain rate effect was more practical.3.The quasi-static loading and compression experiments of Sn0.3Ag0.7Cu solder was carried out by fatigue testing machine at different strain rates and temperatures.The effect of temperature effect on mechanical properties of low silver lead-free solder was investigated,which provided basic experimental data and comparative data for dynamic indentation test considering temperature effect in the future.The experimental results show that the compression resistance of low silver lead-free solder decreases with the increase of temperature and increases with the increase of strain rate.The constitutive equations of flow stress,temperature and strain rate of low silver lead-free solder under different strains were fitted by Arrhenius type equation and the experimental data.The higher the coincidence between the experimental value and the calculated value when the temperature is much lower than the melting point of the solder itself.However,when the temperature is close to the melting point of the solder joint itself,the error between the calculated and experimental values increases with the increase of strain rate.