| The rapid shrinkage of Three-Dimensional IC packaging is driven by the high density of micro solder joints,resulting in an increased volume ratio of Intermetallic Compounds（IMCs）within the joints.IMCs significantly influence the performance of micro solder joints,making the study of IMC growth at the interface a crucial industry focus.This research examines the growth behavior and morphology evolution of Cu-x Ni/Sn interface IMCs,analyzes their growth rules,and discusses the influence of Ni content on IMC growth and morphology.Based on the observed characteristics,a Cu6Ni/（15μm）Sn/Cu6Ni bonding structure is proposed for IMC micro solder joint applications,and the growth behavior of interface IMCs during joint formation is studied.The mechanical properties of IMC micro solder joints are characterized.The findings of this research are as follows:The Ni content in Cu-x Ni/Sn has an extremely significant effect on the growth and morphology of interfacial IMCs in the solid-liquid reaction.With the increase of Ni content in the Cu-Ni alloy pad,the growth rate of IMCs at the interface showed a trend of a sharp increase and then a slow decrease,and the growth rate of IMCs at the Cu6Ni interface reached the peak;the grain morphology of the IMCs at the interface gradually changed from scallop shape to thin rod shape,the solder area dispersed among IMCs grains disappears first,then increases and then decreases,reaching the highest value between IMCs grains at the Cu6Ni/Sn interface.The transformation of IMCs morphology and growth rate is related to the refinement of IMCs grains by Ni,the increase of nucleation number and the stacking growth mode of IMCs grains one by one.In addition,when Ni≥2wt.%,the interfacial Cu3Sn growth is completely inhibited,and the crystal structure transformation of IMCs does not occur.By observing the changes in the morphology and thickness of the Cu-（0,2,6,10）Ni/Sn solid-liquid reaction interface IMCs,it was found that the Ni element significantly changed the growth trend of the Cu-Ni/Sn interface IMCs with different reaction times;With the increase of reaction time,the scallop-like,long-rod-like,short-rod-like and fine short-rod-like grains in the interfacial IMCs change significantly.The significant changes in the growth and morphology of the above-mentioned IMCs are mainly related to the morphology and size of the interface IMC grains,the longitudinal growth mode of the grains,and the number of solder regions in the intermediate IMCs layer.Based on the rapid growth rate of IMCs at the Cu-6Ni/Sn interface and the IMCs phase with a single phase and stable crystal structure,it is proposed to apply Cu-6Ni/Sn/Cu-6Ni in the preparation of IMCs solder joints to solve the problem of current IMCs solder joints existing problems.Through conventional transient liquid-phase bonding,the formation time of all-IMCs solder joints is 100s,which is 12 times faster than the formation time of all-Cu6Sn5 micro solder joints.The tensile strength of the full IMCs solder joints is 87.5Mpa,which has good mechanical reliability. |
