Research On The Mechanical Properties Of 80Au/20Sn Solder Alloy

80Au/20Sn solder alloy is widely used in high power electronics andoptoelectronics packaging in which the mechanical properties of the solder is essentialto meet the reliability analysis of the components. The mechanical properties of casted80Au/20Sn solder were investigated by uniaxial tensile test, uniaxial tensile creep test,nanoindention test, and isothermal low cycle fatigue test.The uniaxial tensile behavior of 80Au/20Sn solder is dependent on thetemperature and strain rate strongly. The gliding fracture at 25℃and low strain rate,transgranular fracture at 25℃and high strain rate, microvoids at 75 and 125℃aredominant. A modified unified viscoplastic Anand constitutive model considering theeffect of temperature and strain rate on parameters was developed. The new modelcan describe the tensile test curves better and can be used in the prediction of the lowcycle fatigue behavior.The obvious creep characteristic of 80Au/20Sn solder alloy was observed at thetensile creep tests.The creep strain rate increases and creep lifetime decreases as theapplied stress level and temperature increase. The experimental data were successfullyfit with Dorn model and Garofalo model. However, the application of Garofalo modelresulted in a lower estimated variance of error terms as compared to the Dorn model.The modifiedθProjection method can describe the entire creep curve, and the K-Rmodel can be used to predict the creep life. Grain boundarysliding is the mostpossible creep mechanism within the given stress level and temperature.The micro-scale thermomechanical behavior of the 80Au/20Sn solder wasinvestigated by constant loading rate/load nanoindention tests. The loading ratesensitivity, obvious size effect, and pile up at 125 and 200 ?C were observed. Thedifferences of the creep stress exponent and creep activation energy obtained amongon the concept of work of indentation, and by the conventional uniaxialtensile/compressive creep tests are small. It indicates that such nanoindention testsand analysis methods can be used to evaluate the creep parameters of solder alloys insome way.The low cycle fatigue behavior is affected significantly by the strain rate andtemperature. The quasi-static tensile character was observed at low strain rate and theinteraction of creep and fatigue dominates at high strain rate in the fatigue tests. TheCoffin-Mason(C-M) model based on plastic strain and the Morrow model based onenergy can be used to predict the fatigue life of the 80Au/20Sn solder. The 80Au/20Sn solder can still resist high alternating stress, so it has superior fatigue-resistantbehavior.