Preparation Of Copper Nanowires Array And Their Micro-joints Applications

With the development of microelectronic products towards high density,miniaturization and multi-function,the 3D Through Silicon Vias(TSV)integration technology has been widely concerned by the industry.The micro-interconnect point is the main structure of the integrated body.With the significant reduction of the scale of the micro-interconnect point,it will face problems: the coplanarity of the solder micro-convex points leads to the structural abnormality of the interconnect or non-contact interconnect points.The large reduction in the volume of solder leads to early fatigue failure of micro-interconnect points.The increase of the volume of brittle Intermetallic Compound(IMC)in the micro-interconnect points leads to brittle failure.In addition,the more functional and miniaturization of flexible electronic products require 3D Through Silicon Vias(TSV)integration,and the current solder interconnect points and IMC interconnect points can not meet its needs.In this paper,copper nanowire array micro-interconnect points are prepared to solve the above problems.In this paper,copper nanowire array was prepared by the combination of template and electroplating,and flexible micro-interconnect points were prepared by hot-press bonding.SEM was used to characterize the microstructure of copper nanowires,and DSC was used to characterize the melting point of electroplated tin layer.The effects of current density,temperature and drying method on copper nanowire arrays were studied.The influence of hot-press bonding process on the bonding between the micro-convex points of the array copper nanowires and the electroplated tin layer was studied.The mechanical and electrical properties of the micro-interconnect points were characterized,and the bending and ductility of the micro-interconnect points were tested.Research on the growth of copper nanowires array shows that: current density of copper nanowires growth rate and significant influence on the uniformity with the current density decreases its growth rate lower growth uniformity and its increase,mainly because of lower current density to the current in the area of electroplating uniform distribution and reduce the growth rate of copper nanowires,makes the copper nanowires growth with high consistency.Temperature also has an effect on the growth rate of copper nanowires.The temperature can drive the diffusion rate of ions in the bath,thus reducing the concentration polarization of copper ions and increasing the activation energy of copper ions,thus improving the growth rate of copper nanowires.The array of copper nanowires with high uniformity and perpendicularity can be prepared by freeze-drying,mainly because freeze-drying can avoid the suction effect of capillary force on copper nanowires in natural drying.The research on the bonding of flexible micro-interconnect points shows that the resistance of the micro-interconnect points continues to decrease with the increase of the bonding pressure.When the bonding pressure increases to 20 N,the resistance no longer changes and remains at about 2.668m?,showing a good electrical conductivity.The reason is that the nanowire array still has the weak coplanarity problem,and the increase of the bonding pressure can make more nanowires with smaller length contact with the substrate to realize the connection,thus reducing the resistance of the flexible micro-interconnect points.The shear test results show that the Cu nanowire array micro-interconnect points with the same interconnect height have higher shear strength than the solder interconnect points,and show a more prominent ductility.Bending fatigue tests show that the micro-interconnect can undergo nearly 1200 times of bending fatigue and still maintain a low resistance.