The Microstructural Evolution And Mechanical Properties Of Oriented Ni Interfaces With IMC

The development of multifunctionality and miniaturization in microelectronic products has driven the rapid increase in the density of micro-solder joints in packaging,resulting in a significant reduction in the scale of micro-solder joints.This has led to a sharp increase in the proportion of interface intermetallic compound（IMC）,which dominate the performance of micro-solder points,highlighting the importance of studying the microstructural evolution of interface IMC.In this study,different oriented single crystal and polycrystalline Ni/Sn samples were used to investigate the microstructural evolution of interface IMC in solid-liquid reactions,analyze the influence of single crystal Ni orientation on the morphology,orientation,and growth of interface IMC,elucidate the regulation of Ni orientation on the morphology and orientation of interface IMC,reveal the growth dynamics of interface IMC on oriented Ni,and test the mechanical properties of interface IMC.The results of the study are as follows:At the（110）Ni solder pad interface,the Ni₃Sn₄grain morphology is a regular flat prism shape,and with increasing reaction time,large-scale Ni₃Sn₄grains dominate the interface.In the case of polycrystalline Ni,the Ni3Sn4 grain morphology is irregular with fine rod and boomerang shapes,and with increasing reaction time,the boomerang-shaped grains become dominant.The（011）Ni and interface Ni₃Sn₄grains exhibit a consistent orientation relationship{1 15}_Ni3Sn4‖{011}_Ni,and<2 81>_Ni3Sn4‖<011>_Ni.This orientation relationship remains constant with increasing reaction time,while there is no obvious orientation relationship for the polycrystalline Ni/Sn interface Ni₃Sn₄grains.The mismatch between Ni and interface Ni₃Sn₄can explain the regular morphology and consistent orientation of single-crystal interface Ni₃Sn₄grains,where the<2 81>direction of the Ni₃Sn₄grain is aligned with the<011>direction of Ni with the lowest mismatch.Compared with polycrystalline Ni/Sn,the growth rate of the single-crystal interface IMC is slower and mainly controlled by bulk diffusion mechanism.The hardness and elastic modulus of Ni₃Sn₄grains are about 5.3GPa and 246.5GPa,respectively.At the initial stage of the reaction,a regular pyramidal-shaped Ni₃Sn₄grain and a small amount of irregular small Ni₃Sn₄grains were formed at the interface of（001）Ni/Sn.With the increase of reaction time,the regular pyramidal-shaped IMC grains almost covered the entire Ni interface after 15 minutes of reaction.The（001）Ni and interface Ni₃Sn₄grains showed consistent orientation relationship:{5 25}_Ni3Sn4‖{001}_Ni,and<553>_Ni3Sn4‖<001>_Ni,and this orientation relationship did not change with the reaction time.The low mismatch between the<553>crystal orientation of Ni₃Sn₄grains and the<001>crystal orientation of Ni is still the main reason for the regular morphology and consistent orientation.The hardness and elastic modulus of the cross-sectional Ni₃Sn₄grains are about 4.5GPa and267GPa,respectively.At the initial stage of the reaction between（111）Ni and Sn,regular pyramidal Ni₃Sn₄grains and a small number of irregular tiny Ni₃Sn₄grains formed at the interface.With increasing reaction time,the regular pyramidal IMC grains gradually occupied the entire Ni interface after 15 minutes of reaction.The consistent orientation relationship between（111）Ni and the interface Ni₃Sn₄grains was observed as follows:{510}_Ni3Sn4‖{111}Ni and<001>_Ni3Sn4‖<111>Ni.This orientation relationship did not change with reaction time.The regular pyramidal Ni₃Sn₄grains were the main reason for the consistent orientation relationship due to the low misfit arrangement of<001>_Ni3Sn4along the<111>Ni direction.The hardness and elastic modulus of the cross-sectional Ni₃Sn₄grains were approximately6.03GPa and 341.06GPa,respectively.These results indicate that single crystal orientations have a strong control over the morphology and orientation of IMC at the interface,but with different outcomes.