Inhomogeneous Growth Of IMC In Cu/Sn/Cu Micro-interconnect Structure And Its Effect On Mechanical Properties

The high-density integration of electronic chips promotes the continuous miniaturization of 3D-TSV packaging interconnection points.The miniaturization process is accompanied by the increasing temperature gradient of the interconnection points.The excessive temperature gradient leads to the non-uniform growth of intermetallic compounds(IMCs)in the microstructure of the micro interconnection points,which further affects the mechanical properties of the micro-interconnection points.Therefore,it has become an urgent problem in the field of microelectronic packaging to explore the IMCs non-uniform growth law and mechanical properties of the interconnection points,especially interconnection height less than 20?m.Cu and Sn will be used as the base material and solder respectively,and the initial Cu/Sn/Cu micro interconnection structure samples will be prepared by self-made fixture and solderless reflow welder,and the Cu/Sn/Cu micro interconnection structure test samples were prepared by temperature gradient and isothermal reflow test platform,respectively.The samples will be analyzed by optical microscope,X-ray diffractometer,scanning electron microscope,electronic universal testing machine and other methods.By keeping the temperature of the hot end constant and only changing the temperature of the cold end,the influence of different interconnection heights on the heterogeneous growth of IMCs in micro-interconnects under the same temperature gradient was studied,and the effect of heterogeneous growth of IMCs on the growth of IMCs was studied.The mechanical properties and fracture mechanism of micro-interconnects with an interconnect height of 15?m.The main research conclusions are as follows:(1)Under a temperature gradient of 2000°C/cm,the Cu/Sn/Cu micro-interconnect with a height of 15 ?m exhibited heterogeneous growth of IMCs at the cold and hot ends of the micro-interconnect.As the bonding time increases,the average thickness of the IMCs at the cold end gradually increases.Full IMCs interconnection points are formed when bonding for7 minutes.The morphology of IMCs gradually evolves from scallop-like to columnar.The thickness and morphology of IMCs at the hot end interface remain basically unchanged;the growth mechanism of IMCs at the cold end interface is reaction rate control,and the hot end interface The growth mechanism of IMCs is grain boundary diffusion control.(2)Under the same temperature gradient,the non-uniformity phenomenon of micro-interconnections with interconnection heights of 15?m,30?m and 50?m shows differences.With the increase of interconnection height,the growth rate of IMCs at the cold end interface gradually decreases.The shape of IMCs after bonding 5min The appearance has also evolved from a pointed prismatic shape to a scallop-like shape.(3)Under the temperature gradient,as the volume ratio of IMCs in the micro-interconnects increases from 20% to 80%,the tensile strength of the micro-interconnects first increases,then decreases and then increases.The tensile strength is the highest when the ratio is 80%.,The fracture mechanism changes from ductile fracture to brittle fracture,and the fracture location is transferred from the solder to the IMCs and finally to the Cu3Sn/Cu6Sn5 interface.The research results of this paper will provide basic experimental data and theoretical references for evaluating and improving the mechanical properties and reliability of micro-interconnects in electronic chip packaging.