Study On Mechanical Properties Of Intermeta Llic Compounds And Thermal Reliability Of Solder Joints

With the development of lead-free and miniaturization of electronic packaging devices,the intermetallic compound(IMC)produced between the solder and the metal to be welded in the packaged device cannot be overlooked in the reliability of solder joints.In this paper,nano-indentation tests were performed on the interfacial intermetallic compound Cu6Sn5 produced after welding Sn3.0Ag0.5Cu.The effects of heating factor on the elastic modulus,hardness and creep of the IMC layer were studied.The elasto-plastic constitutive structure of the IMC layer was obtained.Relationships;The effect of IMC layers with different thickness on the thermal reliability of solder joints was studied.(1)Set the reflow soldering curve with different heating factors to obtain the samples under different practical conditions.Use the continuous stiffness method for nanoindentation test.The effect of different heating factors on hardness and elastic modulus was studied,and the effect of heating factor on creep performance was studied through the retention phase.It was found that under practical conditions,the elastic modulus of the IMC layer is between 80-90Gpa and the hardness is between 2.8-4.1Gpa.With the increase of the heating factor,the elastic modulus of the IMC layer slightly increases,and the effect is not significant.The hardness value of the IMC layer first increases and then decreases;the creep strain rate sensitivity index of the IMC layer increases first and then decreases.Small,indicating that there is an optimized reflow soldering curve in the processing process depending on the operating conditions.(2)Using two different Brinell indenters,based on the load displacement curves obtained from the two sets of nanoindentation techniques,using the dimensionless method to estimate the eigenvalues,and then combining finite element calculations with inversion analysis.The final two sets of characteristic stress and characteristic strain values are obtained;the two sets of stress and strain values are brought into the constitutive equation to obtain the yield stress and the enhancement index,and then the expression of exponential exponential elastoplastic constitutive equation is obtained.(3)The effect of intermetallic IMC layers with different thicknesses on thermal fatigue life of solder joints under thermal cycling loading conditions was studied.According to the actual working conditions,the thickness of the IMC layer is in the range of 0.5?m to 22?m.Ten sets of finite element models for different IMC layer thicknesses are established in this paper.The IMF layer uses the exponentially enhanced elastoplastic constitutive model obtained in the above section.Based on the finite element calculations to obtain the equivalent plastic strain values at key solder joints,a modified Manson-Coffin empirical equation was used to calculate the thermal fatigue life prediction values of the solder joints in ten groups of models,and the thermal fatigue life of the solder joints was established with the thickness of the IMC layer.Based on the functional relationship,the influence of the thickness of the IMC layer on the thermal fatigue life of the solder joint was proposed.